Sorry I’m too lazy to look up a source, but the way I’ve heard it explained is that while they might occasionally give them to sick animals as a sort of panacea, they often just give all of them a low dose. Apparently it like, makes their immune system not have to work as hard so they gain weight faster. Which is basically textbook how to make resistant bacteria.
I believe you can change the scaling algorithm obs uses? Right click the source and go to “scale filter” is what Google is telling me, not at a computer right now. I think it defaults to bicubic which should be ok though? The switch does its own internal scaling a lot of the time and that can look pretty bad though, but unless you get into some serious shenanigans that’s basically baked in.