> Nobody has proven that it's not trainable, so I'd assume that it is.

I've never heard of a successful training regime, or even of anyone who successfully trained it, so that's an evidence against it being trainable.

> And I spend most of my free time on visual hobbies, like playing video games or watching movies. But maybe I'm just attracted to those hobbies, because I'm a visual type.

I'd guess the latter, because I also spend a lot of time on visual hobbies, like playing video games or 3D modelling, and it didn't help me in any way. I still don't have a mind's eye when I'm awake.