I actually think it was the opposite. It is obvious that Luke is catching feels. He is putting more effort in the relationship the more time he spends with Gabriel.
From the look of it, Luke may have suffered from his previous relationships, and he originally believed that Gabriel was only in it for sex, but as they slowly learned more things about each other, Luke learned that Gabriel is a lot more pure than he realized. Angel mentioned that Luke likes the pure type, and Gabriel certainly falls into that category. That is why he fervently defends Gabriel from Angel's harassment.
I think the one way this relationship might fail is that Luke may question if Gabriel really likes him, especially if Ray decided to pursue Gabriel. Luke is not entirely wrong that Gabriel original intention with Luke is more towards lust than love. I do think they will click the longer they date, but uncertainty of each other feeling may linger and be the source of conflict for future chapters.

I am falling so hard for luke with each chapter passing. LUKE BEST BOYFRIEND!
┗( T﹏T )┛
Also Angel is fucked up in the head!!! Really wanna whoop his ass