Alt-Esc works, why can't we pass Alt-Tab to the WM?

[Steven Hurd]

I've noticed numerous threads regarding the use of
Alt-Tab switching in XFree86... to summarize, people
say that passing Alt-Tab through to the WM would
result in users not being able to get back to windows
from full-screen mode.

However, both Alt-Esc and Ctrl-Esc will bring you back
into the windows interface.  So I don't see why Alt-Tab
being OPTIONALLY disabled is an issue.

Could someone please enlighten me?