I can say that the dummy, which has the same 9mm profile as the working unit, was quite difficult to open. I needed to pry the inch-wide bar apart from the rest of the phone's frame to get a grip before I could begin extending the device and unrolling the screen. TCL said that the working unit would have an onscreen button to trigger the sliding mechanism and that people wouldn't be expected or allowed to pull it open themselves. That's probably for the best; I could see people unintentionally ripping this apart with too much force.

That said, I am intrigued by what future iterations of this could enable. It's significantly smaller than folding devices with a similar screen size and seems to offer more protection for the unused screen. The challenge would be coming up with apps that understand when the screen is completely unfurled, or if it is only slightly extended, and then adapting to the different widths.

Without a working demo, though, it was difficult to gauge how effective this setup is. Plus, the industry is still struggling to adapt software for more-conventional foldables like the Galaxy Fold, Moto Razr and Z Flip. It will be a while before people turn their attention to a phone with a rolling, extendable display that's the only one of its kind.

But TCL has been teasing us with foldables for a long time. It showed off its first foldable concepts at least two CESes ago, and those were more conventional designs similar to the Galaxy Fold. The company's general manager of global marketing, Stefan Streit, explained that it's waiting to launch something real because the software simply isn't ready yet. "We don't want to make the user a beta tester for us," he said.

Another reason is cost. TCL's typical MO is to sell affordable options for the more budget-conscious shopper, and folding-screen technology is still too pricey for the mainstream. I admire the restraint and the desire to make something that works, but TCL will continue to lag behind the competition if it keeps waiting.

Of the two TCL concepts, I find the extendable more compelling. But it also gives me more cause for concern. Will it be easier to break than a foldable, because it requires the user to pull it open? How will apps know when a screen is being unrolled, and should they adapt to fit every possible width of the display? These are issues that require more widespread and comprehensive testing to understand.

A wait-and-see approach is safer, but it doesn't guarantee that the resulting products will be better than the competition. For now, it's clear TCL is preparing to do something. What that might be and whether it will be successful remains a mystery.