Where did you see that? It's a funny little expression. It can mean different things to different people. For example, there was this girl on CL who stated that she was providing a "full GFE" but after a few questions, it turned out that she was only offering SGFE. So, I think that if you saw the ad on CL (which has a lot of girls who aren't doing this FT) then for the most part, they are equating full GFE with SGFE (no kissing and/or everything is covered). Whereas pro know what johns mean when they want GFE (kissing and BBBJ) so they only say GFE if they mean it (otherwise it's SGFE).
(There's also the same problem for PSE -- very ambiguous term.)