I used to see the argument a lot in the OSR sphere (... on Google+, so this was a while ago) about how appropriate it was to include non-Original Rules races in D&D. A lot of people feel, to play the game "correctly" (whatever that means) you need to use the originals only.
What's weird is, some of the earliest fan and official material was really, really odd races for D&D. In an early Alarums & Excursions, there was a dragon character class. In the article "My Life as a Werebear: D&D Monster Character Classes" from White Dwarf #17 (Feb/Mar 1980), Lew Pulsipher wrote up rules for one player to play a whole pack of blink dogs. Playing off-type is as traditional as absolutely anything else in D&D.