Yes.So everything you explained would be up to the DM. I was never arguing for potions only adding my opinion to what the rules actually state. But to clarify what I was saying is, like you said the magic is in the liquid, but it's magic. It's not like having already made Kool-aid and then accidentally pouring salt in it would ruin it. Making a potion is basically the same as making a scroll. But let's get off the subject of potions. We both agree that it's mostly stupid.
(Rust monsters rust magical armor perfectly fine though and whatnot)
But yeah. Off topic at this point.