The size must be in the eye of beholder.
For breast size for example, asian average breast is a little above A. Nowaday american average size is between D and DD. So they don't have the same definition of big boobs.
(Ok japanases are particular people as they gave to pornography imagery both loli and extrem thicc female with body propotion no longer seen since dinosaurus extinction).
Some games have big assed female characters with a more "realistic" morphology but with other games female have ass so big that a standard doorway is a no go for them. Both can claim rightfully the tag "big ass".
Maybe adding tags like "extrem/lovecraftian big ass" or "gravity law negation big boobs"... can be a solution.