I suppose its the shier scale of it means they have to reinvent it or it just doesn't work, they were quite open about iCash being a complete failure, it did not work, at all at the scale they need, hence Persistence Entity Streaming, they have talked about the difficulties of all of this but networking is like magik to me, i don't understand it but what i do understand is the nature of a singular game space that is billions of KM large is all directions complete with all the stuff you can fit in that space, multiple plenets.
The 64Bit cordinates system i think was a first when they introduced it in 2017, i don't think its uneque any more, i think Unreal Engine 5 has a 64Bit world cordinates system, it also has, so far as i can tell at least client object container streaming, Ratchet and Clank has something similar to this too, i think. The need to run Star Citizen on an SSD synonimous with it first and long before....
Having said that i have seen a few Unreal Engine 5 space demoes, including one or two who called it Star Citizen in Unreal Engine 5, but whats missing from all of them is the visual reprisentation of going from a blade of grass on planet A in to outer space and from there to a blade of grass on planet B, back in to space and the same for planet C, and then D at all let alone without any "transitioning effects" between, because that's where you hide loadscreens.
As Asmongold put it "ok then do it" I've yet to see it anywhere else.