The real reason why they had no h-scenes with Ama (even in Really? Really!, where she appeared naked and "assisted" in one of Asa's h-scenes) is because her voice actress, YURIA, is also a singer of some repute and doesn't want porn-star acting to tarnish her reputation.
Apparently, many other famous anime voice actors go by pseudonyms (false identities) when acting in h-games. It seems this wasn't enough for her.