It is also intermittent. It appeared with a vengeance at SU9 launch. Then recently disappeared shortly after the special Xbox 1.25.12.0 patch. Then, reappeared in the last two days.
I know no one wants to read the thread, but this is documented through this horribly long thread:
I have two Xboxes. I didn’t install Top Gun on one and it gets the same message as the one that I did install it on.
It seems unrelated to anything I”ve installed in the recent past. I never use the sim on this one Xbox, so the last thing installed here was 1.25.12.0 and that was via the Xbox OS rather than the Content Manager.
I will say this much, booting the sim will sometimes result in seeing the Installation Manager appearing shortly after the Asobo and Black Shark AI screens. If that does appear, then the Download Completed message will appear.
If it boots and the Installation Manager does not appear, then I don’t see the message.