While communication from Microsoft about its layoffs and reorganization lacks a certain amount of clarity, one statement made in its earnings call yesterday did appear to be straightforward: "We will streamline the next version of Windows from three operating systems into one single converged operating system for screens of all sizes" said CEO Satya Nadella.

The immediate reaction was twofold. From some parties, there were congratulatory noises, praising Nadella for this new strategy that moved away from the Ballmer-era multiple operating system. From others, there was glee that the "confusing" line-up of Windows, Windows RT, and Windows Phone would soon be gone and that in the future users would no longer need to worry about what their devices were using. Some are even cheering the "fact" that this means that Windows RT will be killed off forever.

That Nadella's remarks provoked headlines and column inches is ever so surprising, however, because what he said isn't new, isn't really being interpreted properly, and wasn't really his idea.

Yes, Microsoft is developing "one" operating system. But that's not a new Nadella-era policy. In the July 2013 reorganization performed by former CEO Steve Ballmer, all operating system development was combined into a single Operating Systems Engineering Group, headed by Terry Myerson.

The core of that operating system is now used in Windows Phone, Xbox One, Windows and Windows RT tablets, Windows PCs, and Windows Server systems. The operating system isn't completely identical across all of those variants—the phone and console both have special user interfaces, for example—but core features like the kernel, security model, and major APIs are the same.

Some of the differences are usage-driven. Windows Server sets some tuning parameters differently from Windows on the desktop because Windows Server is used for background services rather than as an interactive client operating system; Windows Phone has a somewhat pared down API and no desktop because it's designed for use on slow processors with 512MB RAM, 4GB storage, and a four-inch touch screen.

Other differences are driven by market segmentation or support concerns. Desktop Windows can't be used as a server, and Windows RT, for ARM tablets, will only run desktop applications that have Microsoft's digital signature.

These differences may in some sense be artificial, imposed not by any technical concern but rather by the economics of Microsoft's business. Still, they're not going to go away. Nadella said as much in the call; Windows will continue to have a range of SKUs with different prices and different features to address different market segments.

Similarly, the technical differences aren't going to be going away any time soon. It's feasible that Microsoft will ditch the "Windows RT" brand name for Windows compiled to run on ARM processors, but that won't magically enable Windows-on-ARM to run existing x86 software, and it doesn't mean that Windows-on-ARM is going away. The Windows desktop may be important for desktop and laptop users, but we're not going to see it on phones any time soon, because it's simply not designed for small screens and fingertips.

As such, the idea that the allegedly confusing set of operating systems is going to go away is ill-conceived. The names may change, but the differences won't; the operating systems will look different and support different applications, and we're highly unlikely to ever see x86 desktop applications running on ARM Windows Phones. From the practical end-user perspective, there are going to be just as many Microsoft operating systems as there ever were.

What will happen is that there will be a single application model that can span Windows and Windows Phone, and in all likelihood, Xbox, too. Again, this isn't news. We know this already, because it's more or less shipping already. With Windows 8.1 and Windows Phone 8.1, developers can share a large proportion of code between their apps, with many applications needing only user interface adjustments to tackle the different operating systems.

These Universal Apps were extensively detailed at the BUILD developer conference this year, and the company gave strong hints that sooner or later, Xbox One would be a third Universal App platform.

Related to this are changes that have either already occurred or at least been previously revealed. Microsoft unified its developer portals, documentation, and registration program (some of those changes happening just last week), and news of a single app store leaked last year.

And while it was Satya Nadella who made the comments on the financial call, these aren't new Nadella-era policies. They were all put into motion during Ballmer's time as CEO, and in fact Ballmer explicitly described the way Windows would evolve. Talking at the Gartner Symposium 2013 last October, he clearly described how "Windows Everywhere" would work, with a common developer platform, common user interface concepts (but tailored to different form factors and devices), and common services across all devices. The new organizational structure and its unified operating system team was put together to enable this, and, Ballmer said, the results would be delivered relatively soon.

Even before that, the notion of "three screens and a cloud" championed by former Microsoft Chief Software Architect Ray Ozzie presaged this development, with the idea that Windows and its apps would span smartphones, PCs, and TVs. The tablet adds a fourth screen, but the concept is the same.

Nadella's "single converged operating system" isn't a new idea: it's the restatement of Ballmer's "Windows Everywhere" dream and a continuation of work that happened during his reign. It's a sensible dream, and it's a dream that's becoming ever more real. It's just not new.