Hard to tell from the outside.

BE-4 took slightly longer than expected and required the big test stand. BE-3 fits the small stand, it was developed on it. Much easier to work in parallel.



Another idea is that the date at wich the new rockets have to be able to deliver to all reference orbits was earlier as expected. So no time to do BE-4U now and then follow with the BE-3U 3rd stage for the high performance targets.



Then there is always customer demand. After the NG reveal there must have been a lot of talks with prospective customers. What crazy ideas did they have? Who is (probably) willing to pay for them? Blue certainly has ideas what to do with NG - if they can align them with customer demand things should get a bit more streamlined. See the 5 meter fairing, no actual need to build and qualify it.



I still think that Jeff is a bit more likely than Elon to go the quid pro quo route. He certainly has the money and tries to play the long game. Getting what was talked about is as good as getting ammunition because the other side did not deliver. All that of course only as long as it is not too much of a detour from the internal goals Blue has for the rockets and as an organisation.