>I believe I already mentioned it in that post, and it's also depicted there. Is there a distinction between those terms?
Assuming you meant "Japanese AV", AV = hardcore pr0n, whereas gravure idols are more akin to glamour models. They often have videos released that are highly erotic, featuring upskirt shots, bewb massages, etc. ヽ(´∇`)ノ

>I feel frustrated because it's inconvenient to hide on these underground or less-known websites
Conversely, underground and lesser-known is how teh web should be