Are "love boners" a real thing?

I'm dating a guy who had a boner when I said to him that I was in love with him (and viceversa). Nothing in that moment was sexual, we were talking just about life. When I asked him why, he told me that it was because it was an emotional moment. Before and after that he was normal.

Nobody before him has told me that. I saw that there are some infos in google but not enough. Do you have any experience with that?