There is a difference. I believe the "flying fox" is far more lazy than the SAE. And it also doesn't eat the same algae.
A real SAE, can be distinguished from a Flying Fox by its stripe. The flying fox has sharp/straight edges, whereas the SAE has a jagged edge, like shark teeth. Haven't look into this part, but I've read in a few cases that SAE's have a tan line above the black line.
Also, in petshops, they are often wrongly labelled. So remember to check.
HTH