Firstly, the body raises most of the growth factors naturally and considerably, but especially so testosterone, in response to muscle mass stimulated by weight lifting.
Secondly, there are studies out there that show considerable growth (of small an micro-penises) by testosterone cream alone.
Thirdly, PE works as evident by this forum.
I would say the default position is, that stuff just grows the more its stimulated and exposed to growth factors. And does less so if it isn’t. Any other proposition would be kind of strange.