It might be helpful for you to read a post about Love vs. Luuurv (the fantasy) that is currently on the WS forum.
I can't claim to know the exact feelings you H had in his heart nor the reasons behind them but in my own situation, I can see in hindsight that I was using "I love you" as the proxy statement for a whole lot of other things.
Without the benefit of the past 6 years of self-examination and self-reflection, the phrase "I love you" came out because it just felt like the right thing to say. It felt like love but in reality, it was a lot of self-medication to heal the trauma of breaking up with my xgf some 30 years before.
There is a difference between being in love and feeling in love. The infamous phrase, I love you but I am not in love wiht you has its roots in that subtle difference. And it also exists within the framework of the affair. We wanted to be in love, we hopped we were in love, we thought we were in love but in reality, it was luuurv. And luuurv can't and doesn't survive the light of day. Only real love does that.
You could also post this question in the I can Relate forum in the Questions for the WS's thread to get different relies from other WS's.
Unknown Poster - The mind of a WS is a very sordid, confused place during the preamble, main body, and post mortem of an A. Don't give us too much credit for rational thought.