good point, however by not having direct information on this we can only use typical explanations such as mew being a baby god, does any other Pokemon benefit from this
mew is the unknown of Pokemon, even arceus is only god of certain dimensions not god of ALL known Pokemon, I know this through
[SOURCE of arceus]
mew was also tampered with, it was shown in Pokemon first series to be pregnant, didn't give birth to mewtwo however it shows mew can carry. perhaps mew was the splice gene of arceus which can also learn moves however in a different method such as learning OP moves at later stages and being the essential type switching Pokemon. mew can tap any. does it matter whethere mew can learn a move every 10 levels or that mew can learn anything.