Now you're just getting picky. Neo-Geo strays pretty far from norms. It's effectively the only console with two physically/electronically different cartridge formats, but with the same ROM chips. A conversion involves taking chips from one cart and putting them into another. Anything else is a bootleg. Neo-Geo also wields insane prices, causing people to do anything to swipe those big bucks.
But, I do know that the sole purpose of mask ROM conversions is to scam people. From that perspective, you're free to call any non-legitimate AES cart a bootleg or fake, regardless of how fake it is. Personally, a mask ROM conversion is a lot more legitimate than an EPROM cart.