i don't know your friend but i'm kinda like that too i don't intend on getting speech therapy or continuing the exercises i've been doing you just reach a place of forced acceptance where yeah it's anxiety inducing to stutter but fighting it makes it worse and you just stop caring basically your friend is probably at that stage too, maybe he gets anxious about it but it's also very freeing, so not caring on your side is a good thing you make him feel safe enough that he doesn't give a shit, that's a good thing :)