I guess that will happen, when they have a functioning system, i.e. a product. (Showing off with some in-between, not fit for purpose stage may be deemed somewhat embarassing, compare cultural differences.)
Its not cultural. Lots of European aerospace startups act not much different then American ones. In some cases they are even more over the top then American startups.
This is more about ESA culture then European culture in general.
Well, startups are not actually a mainstay of European cultural tradition… ;-)
On the other hand, more traditional enterprises, like, say, Mercedes Benz, will be quite cautious with claims about their R&D, until they have their level III autonomous car system actually approved (and even then… don't make too much of a fuzz, as it is still limited, etc…)
Or, for another Tesla comparison, take Citroën (that is, Stellantis): While Tesla keeps on going about how there will be an affordable EV someday, thus they are saving the world now (without anything like this even being in sight), Citroën actually launched the Ami (an electric 2CV equivalent at EUR 6,900.) And they didn't talk about this before the launch, either. (Then there was a short-lived publicity fuzz – and then they mostly forgot about it. That's quite a genuine example for how European enterprises think, showing off appropriately works.)
To make this a fair questions, please include, "how many cheap Teslas are there to date?"
(It somewhat boils down to, US firms have something which may be called "anticipatory marketing", which is deemed rather off-limits for European organisations. To the least, you'd paint quite a big bull's eye onto yourself.)
This is more about ESA culture then European culture in general.