Yeah, I don't think you are fully understanding things here.I agree. I mean, I can see the logic behind the process, but I don't think a pokémon like Yanmega should be made UU without a previous test. Nobody uses normal Deoxys in Ubers, should it go to OU?
What if everybody stopped using Scizor? Would it be UU until voted otherwise?
If something like Froslass is currently a Suspect, I don't understand how Yanmega is being allowed.
Yanmega is getting tested in a sense. When it goes to UU, people will be observing whether they think it should be banned or not. If they think it should be, they will remove it from the metagame and evaluate the findings.
Ultimately, I don't think it matters which way it's done, as the eventual outcome should end up the same. I personally much prefer doing it the way that we're doing it now.
Ubers isn't a usage tier. It's a ban tier, or a 'faux tier', rather like BL. Infact, some won't even call it a tier. If something literally never gets used in Ubers (like Wynaut), it won't drop to OU. However much an Uber gets used in Ubers, it's still too broken for OU.
And yes, if everybody did stop using Scizor, it would be voted UU until otherwize. This is because OU is a usage tier (OU means 'OverUsed'). It is determined solely by how much a Pokemon is used, so if Scizor didn't get used, it wouldn't be OU, because it, well, isn't OU! A few Pokemon aren't considered very good, but are OU, because the statistics say they are. With something like Scizor, it'd most likely be 'obviously' broken in UU, so the testing would be sped-up considerably.
Your statement about Froslass doesn't really make sense. To people who lack knowledge of competitive battling, Rampardos may seem too good for UU, and it clearly isn't. Likewize, Yanmega may seem too good, but we won't truly know how good it is until we test it.