I think people were going to buy Origins regardless, because of a Retro Engine S3&K, but Chaotix would have been a great addition for the novelty factor. AFAIK that game hasn't had any re-release ever? So it'd be great to have it on something that isn't a Sega 32X.
But, if it's purely Sonic "Origins", then no, it doesn't really belong. Then again, when did Vectorman ever belong in Sonic Mega Collection, so it's a moot point.