I hope this is a mistake but since we were discussing this in the Beholder thread about the non-inclusion of Yuan-Ti in the final SRD, I had to post this. In the online art gallery for Races of Faerun, this picture is labeled as Yuan-Ti:
Could this explain the absence? They are redefining the race to make it Faerun-specific?

Could this explain the absence? They are redefining the race to make it Faerun-specific?