CE, You definitely might be right that Mr LFL is somewhat turned on by the idea of LFL with someone else.
However I wonder if it is just as likely that the thought of LFL being with someone else triggers more of a feeling of "I will be the man my wife needs and wants. I'll show her how I really feel about her."
There is something about the way LFL writes about her H which makes him seem more Alpha and stronger to me than she seems to see him.
I wonder if LFL has taken the time to sidle up to him today and let him know exactly how great yesterday was for her. As in whispering in his ear "I couldn't stop thinking about x, y and z all day today." or whatever...
I think he does want to show me he wants to be my man. When we were having sex last time, he did more talking again. Sort of angrily whispered "you're mine" (but in a hot way) and then kept going "say it...say it...say it..." until I said it back to him. It was so not like him. He's never possessive like that. So yep, he definitely has alpha traits in him that I have just been overlooking.