As far as I know, 꽃돼지 doesn't mean 산돼지 or 멧돼지. When 꽃 is used as a prefix, it usually means beautiful and vibrant. So it's sometimes used to refer to a person or animal who is plump in a very likable way, especially when they're young. If you call someone just 돼지 (and also 멧돼지 and 산돼지), it usually sounds negative, but adding the prefix 꽃 makes it positive, like they look nice, cute, or good some other way. There might be other uses, but this is one use of the term I know.

i guess 꽃돼지=묏돝=산돼지 ))