I'm kind of on the fence for this.
Garazza is right though, they are rivals first and foremost (or frenemies in Flatlines case XD). Sure some rivals grow romantic feelings for each other, but that takes a few arcs worth of development and relationship building.
The kid barely understands his own feelings. Back in TT he was acting OOC while around Djinn, like being particularly nice to her, complimenting her, hell he pulled a Steve Rogers and jumped on an explosive for her.
To him, that was how he showed affection.
Even Emiko called Djinn out because Robin was making rash decisions when she was involved (To which Discount Raven had a very violent reaction. Didn't she also erase Emi's memory?). She had no issue ragdolling and mindwiping Emi when her emotions were running high, what are the chances she could've also been manipulating Dami because of her feelings. I've always felt that it might be Djinn unconsciously manipulating him, from the moment they met and he asked for her help - she became attached to him. (That's just a theory though.)
Even as Dietrich said, Damian states that whatever he and Djinn had between them was gone at the end. He couldn't define it as a romantic relationship because he doesn't understand what that is.
The only actual times we get something solid is that kiss and when Heretic called Djinn his "Beloved".
This is Bruce Wayne's child were talking about. Feelings might take some time to understand. Although, with Rose and Flatline in the picture, I can easily see him gradually learning. He's not gonna go full Romeo anytime soon, but towards the end of the tournament arc I could definitely see him developing a bond with Flatline that might be potentially more than friendship (Plus, I just love her character thus far XD)