Do any quiet BPD males here silently stalk their person of interest?

My friend who is male also has BPD but the quiet type, whereas my BPD manifests outward in full force. I've noticed some strange things about him but i know if i ask directly he won't answer. There is a person i know he is somewhat interested in or has had feelings for in the past, he gets the opportunity to talk to her as she tries to approach him quite often, however his replies are super short and almost always have an air of nervous out of place laughter (like laughing at everything, even stuff that isn't humor related).

Despite having so many opportunities to talk to her and its clear he wants to be around her because i will sometimes catch him staring at her wide eyed with an expressionless  almost vacant look, he seems to keep her at length, but will silently stalk her on social media, he won't like or heart or react etc to anything but he watches everything she does, all her posts, pictures, updates , even when she follows or likes someone on social media he will follow them too. 

It's odd because he could directly speak with her... it's clear to me that she takes somewhat of an interest in him yet he prefers to just silently stalk her and i don't understand it. He isn't vocal about his silent stalking XD I just notice it because we are close friends. 

I'm trying to understand the reasoning behind it tbh. If i am fond of someone or like them my expressions become loud and i can become stalkerish like i will like everything they post and try to talk to them or cling onto them anytime i see them but i know i do this and i'm forward about it too...but i think i also get away with it easily because i'm a female &gt; . &lt; also most people just tell me i'm cute, so i guess i'm less perceived as a threat, than a man might be. 

But i don't understand why he doesn't just approach her more directly when they are already friends at a distance. 

Explain this to me. Have you been in a similar circumstance? What would you do? and what is ur reasoning behind this behavior. 

I'm trying to understand my friend as well.. sometimes i struggle, i wish i could help him more, sometimes he does lean on me more to introduce him to others, since i come off as more social. But he is very well capable of being social as well once introduced to people. 

Thank You In Advance for all your responses!! &lt;3