First off, pet peeve of mine, it's biceps, not bicep. Any of the 'ceps muscles have the S at the end in the singular as well as the plural.
It's very possible that his bicep developed like that because of poor workout habits when he started lifting. Where I grew up, a South Texas trailer park in the 80s-90s, there were lots of guys who had knotty, malformed biceps like that, and the vast majority of them were a result of poor, or most likely non existent stretching regimens.
Of course his right triceps looks just like mine, the way it sticks out at an almost pointy angle - mine is from a bone graft surgery on my right humerus. So something like that might have caused the malformation of those muscle groups too.
Stretching? Haha, no. That does not cause biceps looking like that. And the reason the biceps is called BICEPS is because "it" is really a "they", it's two muscles (long and short head).