>>713871423i knew that, and even know the kanji for it
wario is clever because w is a flipped m and in moon it's a pun like you point out by swapping out the ma- with a wa-
luigi on the other hand is ru-i-ji, the ru- isn't a syllable with an "a" sound, and thus it isn't clever to prepend a wa-. it's just clunky sounding.