Learning can mean anything from people that have never seen it, to working to get that last phase down.
Clear SHOULD mean that everyone's confident with the mechanics and just need that's clean enough to not enrage.
Farm SHOULD mean 1/2 the part doesn't hit the floor during the fight, but that doesn't always happen.

At this point, some of us are skilled and geared enough to carry 1-2 severely underperforming DPS and still manage to clear things, so that's not always what you get. Some "clear party" people might have gotten their underperforming butts carried to an enrage and now think they're good enough to clear. Then when they do miraculously get carried through a clear, they jump into a farm party and wreck that by not knowing what they're doing.

In other words, you can get a bad egg in any of the 3. You might also get a learning party where 1/2 of us are veterans, and you end up clearing in a few pulls even when there are one or two people that messed up.