1st:Not even commenting on the validity of your argument, all this does is prove my point. You compared the sets, not the uses of Beat Up which you really can't compare because they serve different functions. Weavile might be a better Pokemon than Ambipom but you can't say it's a better user of Beat Up because Weavile would spam it, Ambipom uses it selectively to bypass counters. I mean I honestly don't understand how proving Weavile is a better Pokemon proves anything regarding its usage of a coverage move.
But I have several bones to pick with the content of your argument anyways. Like how they use Beat Up differently, the two Pokemon play differently. First off, Weavile might have higher Attack, but Ambipom actually hits harder because it has access to Return which is significantly stronger than Weavile's STABs. Second, Normal isn't a terrible STAB in UU when you have high powered Dark and Fighting moves for coverage. Finally, the two Pokemon occupy similar but different team niches. They're both fast and frail attackers, but Weavile's best set is a late game cleaner that plows through weakened teams, Ambipom focuses on screwing up offense with Fake Out (much stronger than Ice Shard, and with flinch it plays differently) early and mid game. Objectively Weavile might be a better Pokemon, I haven't used either enough to pass judgement on that. But its silly to say that Ambipom sucks because Weavile is good, and its sillier to say Ambipom sucks because Weavile can use its coverage move as a gimmick STAB.
How can you argue Ambipom's case if you haven't really used it? In my experience w/ using Ambipom, it gives too many things excuses to come in, is forced out ridiculously easily and forces the user to make a prediction all too often to be truly good in its own right. It also, unlike other pokes has to run life orb to be any use at all, meaning it always hurts itself to attack. Banded could slightly help with a surprise factor but that' about it and silk scarf last resort, well... let's just say that using that set is about as close as you can get to shooting yourself in the foot in the uu metagme.BTW I'm not a fan of comparing these 2 since weavile and Ambipom are certainly different in many aspects cuz fake out, swords dance, ice shard etc. but I feel this comparison necessary to get my previous point across