Fl said he dated plenty tho. And if that's his reason, what's with the double standards lol? Didn't he shoo away all of the guys who wanted to confess to fl with his ambiguous attitude with the fl? Didn't he think fl would want to practice like he would?
Frankly my guess is ml is aware or is deliberately being dumb with how he likes fl. He just didn't make a move bc of his family trauma. He sees fl as his family and if he confesses and fl rejects him, he'll possibly lose that closest person to him. Didn't his family neglect and lowkey abandon him when he was a kid? He might fear abandonment.
There's also a slight possibility that he likes fl's sister and he confessed the night after that csat. But I sure do hope we won't get this mess

Imagine if his reasoning for kissing her sister is bc he wanted experience/practice, and bc her sister is the closet person who looks like FL.