Yep. If you go and register a new gmail account today, there will likely be no option to enable IMAP access for that account, altogether.
(I did a spike development for OAuth and a separate investigation into Labels when I had some free time).
So they are definitely not nice IMAP citizens.
Oh and then there's the issues with Labels that their own documentation apparently gets wrong...
If it's still not standardized then the pitchforks are aimed in the wrong direction.
Because, IIRC, IMAP access must be explicitly enabled by going to Settings -> Forwarding and POP/IMAP -> IMAP access: (o) Enable IMAP. And I think it is not enabled by default.