Generally, GFE implies some kind of tenderness similar to what a gf would do during love making. It seems to have become a euphonism for (french) kissing. The argument that a gf would never give a covered bj is fallacious because a gf friend doesn't charge by the hour either!! (Although you do pay in other ways!!).
So people don't ever forget that the tenderness (or domination or submission or agression or whatever you are having yourself) is SIMULATED. We punters are living out a fantasy - she isn't a real gf or mistress or slave or whatever - comparisons with the real thing don't hold.
Capiche?