Bug explanation
It seems the AutoSuggestBox is having some issues. The layout in the demo app (Fields page) is not ideal, and there also appears to be an issue with the outlined style (hint text is displayed twice).
UPDATE: Checking out the commit (9be7c3d) where the PR merged to master (in detached HEAD state), I can see the same issue. So it would appear it has been like this on main since it merged.

Version
5.0.0