Well, he does feel what she feels so I can't imagine him taking lightly the idea of smothering himself with the sensation of tentacle dicks.
Let alone having one shoved in his mouth.
Exactly why it's more like masturbation. I can't quite describe it, but I guess it's like what you said, he feel what she feels, so it's like double-the-feel or something. Kinda hard to explain about it, especially the one about the mouth, but maybe you can cut it in the fact that he got twice the sensation and leave it there? :Y
