http://bugs.winehq.org/show_bug.cgi?id=15920
--- Comment #1 from Vitaliy Margolen vitaliy@kievinfo.com 2008-11-06 08:51:28 --- Wine asks for the best matching resolution. Check output of 'xrandr' for the complete list of those resolutions.
Since you don't explicitly specify allowed resolutions in the xorg.conf you leave it up to X server and driver to pick them.