I have re-created your test project:
And with pretty much the same result.
I added names to the buses themselves, as I thought that may be the problem, but it does not help (much?).
I get “only” 16 ERC Violations of the type “Error: Label not connected to anything”
Here is the project if you want to see for yourself:
2022-11-13_asdf_bus_vector.zip (16.2 KB)
A few months ago I made a more complicated test project for buses, and I think it was bug-free back then, but now it throws 25 "“Error: Label not connected to anything” violations.
2022-07-09_asdf_hierarchical.zip (26.3 KB)
My best guess is it’s a bug in KiCad, introduced after July, but I do not have enough experience with buses in KiCad to be sure.
Just 3 weeks ago there was another user here with a very similar situation: