Off-topic, but as a non-native speaker I’m curious if it’s common to say “more and more slow” as opposed to “slower and slower” (maybe to emphasize the adjective?)
I think it's just not actually technically wrong in the first place, merely uncommon because it's a little awkward.
What makes it ok is it can be used deliberately to build imagery or to intentionally trigger thought because you have to stop to parse it.
What makes it "wrong" is exactly that having to stop to parse it. It's obfuscated meaning to say "increase the decrease". A decrease is a property that may be increased, so it's legal, but you have to stop to puzzle it out rather than know what it means instantly without thought.