thankfully no, if LFS sold smaller green morays then a lot of people would buy then and put them in 40, 55, and 75g tanks and then end up killing the green moray. Thankfully only larger specimens are usually offered in stores.
According to my LFS guru they're easier to transport/acclimate as they mature, and so he rarely gets one under a foot and a half or so. There is also a stronger market for large green morays, being as though I've seen them up to $400 each, people don't want to spend that much on a smaller specimen.