The only reason to use the "broken-by-match" definition is for some philosophical weirdness where one feels the need to treat the suspect tests literally like a trial. "Who is guilty?" Yet, the people who have taken this approach have failed to see the whole point, which is simply to improve the game substantially. This is supposed to be the replacement to grandfathering Gen IV thinking? People also reference "Smogon policy" when, again, said policy becomes vaguer and more open to interpretation by the day, and just from reading the posts of badged users it's clear that the way in which "Smogon policy" is being invoked right now isn't necessarily being followed. In fact, when people reference "Smogon policy", they tend to grandfather the interpretation from Gen IV!
How is it that completely decimating a playstyle improves any game? In what way does an action like that create a balanced or diverse metagame?
If we were to ban Drizzle, Rain Offense, something that has now overbalanced the entire metagame because of it's brokeness, will disappear, creating a massive unpredictable shift in the metagame towards something that could quite possibly be far worse than Rain. I can easily foresee a strong unrelented push of Sand Teams in the wake of a Drizzle ban, simply for how naturally powerful they are, and how unreliant they are on the weather (bar Doryuuzu). At the same time, entirely eliminating the playstyle of Rain Offense seems a bit drastic considering we are trying to create a more diverse metagame. Considering how core that it is to the current meta, we have no idea what could possibly fill the hole it will leave. It could be filled with one thing or perhaps a great many things, but no predictable diversity will arise, so how can this be a goal with this ban? However, one thing does remain sure: banning the abusers keeps the control of the metagame in our hands. It keeps a check within the metagame that reins in the aforementioned seen or unforeseen threats so that they don't become overwhelming, and keeps the diversity level of the metagame status quo or better, whilst still balancing the metagame in one way or another, thus making it more balanced than the alternative option of simply banning Drizzle.
At least, it creates this sense of "more balance" for the immediate future. This is important to note, as we don't know how banning one thing over another in a situation like this will effect the entirety of this metagame. We can be sure that our desired result will happen, but we can't be sure about what the rest of the metagame would look like. And how can we? How can we be sure that the ban we chose was the better one? What tells us that banning Drizzle now creates a more diverse metagame later on, two, three, four more bans from now? What tells us that banning the abusers creates a more diverse metagame later on, two, three, four more bans from now? Frankly, I can't answer these questions myself, and I'd be impressed if anyone could. To be honest, I find this to be the fundamental flaw of the new system that we use. The metagame right now is so imblanced, that it can turn on a dime depending on which ban we implement, and could still be completely overcentralized. No option right now creates a "better" metagame outside the fact there is one less problem. Personally, I think either way we ban will lead to a superior metagame. But I'd still rather be sure-footed in our bans, so that we don't leave loose ends just lying around. So I say, for now, ban only what's broken, just as we have for generations previously. This has been our system for so long simply for the fact that it works.