All I can do is to share my own experience (as the spouse of an alcoholic): First, guys love porn. The old joke is: "70% of men watch internet porn at work, and the other 30% are lying." So there's that.
Second, while my wife was drinking, I definitely used porn (looking at pictures on the web in my particular case) as a distraction. As a way to not be present. It may not have risen to the level of an addiction, but it was totally and completely obsessive.
I like keepthefaith's suggestion that he discuss this issue with his sponsor. Rigorous honesty and all that. The other great thing about being in a program is that both of you can learn to have actual conversations again...so try talking to him. It sounds like you're pretty comfortable not being overly judgmental about the whole thing...so just express that you have a concern and then let him tell you what he's thinking and feeling.
Good luck.
PS I also like keepthefaith's other comment: "Are you actively working your own recovery?"