Perhaps he experienced one or more traumatic events that included relationship loss for which he blames his not providing emotional and sexual intimacy. Holding that trauma would make him less able to be present for his own satisfaction. He may believe at some level that he's undeserving.

You could consider offering to treat him as the receiver and listen to and look for any discomfort. He may need therapy. If he's worth it in other regards, you could invest in a couple's portion after he's worked some of his individual issues. Devotion like he's offering is a rare thing. Only you can decide if you can tolerate this neurosis.

It seems to me that we can only have feeling for someone from the image that we have created in our own mind. We see some reality truthfully, but we add much of our own filters of desires and ideals. Others filter themselves because of what they don't see in themselves and they put their best face forward often and especially in the beginnings of relationship. ("The Four Agreements" by Don Miguel Ruiz describes our human condition well.)
I think it's a risk of life in general.
It is much easier to oversell yourself or even take on attributes that aren't you when your not in-person. The body language, facial expressions and other subtleties of direct dialog are missing.