https://bugs.winehq.org/show_bug.cgi?id=49933
--- Comment #3 from Rafał Mużyło galtgendo@o2.pl --- 'fixme:...: stub!' is just a standard content for just about any stubbed function. In this context, 'fixme' is little but debug level; some of those functions do need to be implemented, others - not so much.
Anyway, if a window gets marked as always on bottom, Alt-Tab isn't supposed to bring it up.
Your problem seems to be that in the installers you've tested, it's marked as such incorrectly.
...I can't recall whether I've seen a duplicate bug and/or seen that once or twice awhile ago...