Sorry brother you have wrong belief. I have seen many people including me same thing which you are talking. Its not about masturbation.
Hairs dont grow evenly at all places in our body. Sometimes moutache grow first then beard starts growing. The hairs in underarms grows later. Actualy its all fucked up.
Dont worry. It will grow fully till then just go with your current looks.
My friend who said you need a beard to be you u should be happy because you are special from them everyone has a beard but u have a more proffesional look so i say dont care about anyone and work on yourself and that begins with good habbits best of luck friend
Yo bro you are 16. Im 21 and my facial hair isnt growing the same at all places. Who cares man. There is no connection between Testosterone and facial hair. My Seargent also always told me, if you have a beard your gasmask won’t close properly