Phoenix tangles his legs into Alec's as he cuddles in closer. Envy or jealousy aren't a part of his psychological make-up. If Alec were talking about a lover he missed, and still loved.. it wouldn't matter, Phoenix would even be willing to help them speak.

It's purely the fact that it might be a false emotion, and that Alec can't tell, and that Lorac sounds dangerous and quite capable of harming Alec.

"I'm glad I know I love you." He whispers. "I'm glad it's real."