Agreed, and too bad. The Core Settings (FR, Eb, "PoL-Land") can be a polyglot melting pot if that's what WotC wants, but other campaign settings should be free to play by different rules. No aquatic elves in Dark Sun, for instance.
If a DM took his Eb group (including an elf Chr-rogue) and forcably dropped them in Ravenloft to a greeting of "surprise, you're character is now useless", that would be Not Cool (TM). But with informed consent where everyone makes their characters in full knowledge of how the setting works no one would have to be "forced" into that situation.
That being said, WotC also has rule of "No bad choices", which I'm fine with as far as game design goes. It may be just easier to say "Look, Ravenloft is a xenophobic place. Don't make a character that 'looks funny' if you don't want them to get lynched."
I can hope, anyway.