Good question, if the guy/girl is in on it i wouldnt call it cheating, if hes holding her hand there while she is getting eaten, it seems a bit like its a fair game for both,
Or mabe hes letting her have some kind of kinky fantasy, and just enjoing the show.
like i know a cuople(old friends), where the bf likes to sit on the sideline and watch while hes gf is getting nailed by other guy or girl "friends", even withouth him doing anything att all, normal for them super weird for others, guess we all have some kind of weird ass fetishes, so whats going on in that video is realy hard to tell
sorry for the long reply and trash english but there it is hehe..friday lonetime