'Tis true. I remembered this after trying to export a 2k+ unorthodox file in MPEG2. You can change the 'Preview File Format' of a sequence when you make a new sequence by changing the editing mode to Desktop(windows) or Custom(osx) but even then you'll have to pic the right AVI or QUICKTIME codec... so... if you can preview without rendering you should be good and when you're exporting don't check the "Use Previews" button.
