yeah, of course it's going to be secondary if it's in a fic that's primarily arthur/merlin. but even in those fics, it's not usually a device to get gwen out of the way. there is definitely some gwen/morgana show-canon support and there are many devotees to the pairing and many primarily gwen/morgana fics. no, not nearly as many as there are a/m, but i've been kind of pleased to see how much love there is for the lady-pairing in this fandom so far.