Unless you're a bike mechanic, or unusually attentive, you probably don't really know what a bike looks like or how it works. You have some of the basic ideas but not enough to wire it together. So, when people draw a bicycle from memory what they draw doesn't really make sense from a mechanical perspective. The bikes they draw couldn't work. It's not about being good or bad at drawing, it's a question of "are you poorly drawing a workable bike, or are you poorly drawing a nonsense contraption?"

If you could visualize a bike then you'd be drawing a poorly drawn bike that was fundamentally correct. As you cannot you just draw the same abstractions that I might. e.g. I know there are handlebars, pedals, wheels, connected together by metal poles. The fact that your drawing would be very different if you had a photo of the bike in front of you when you were drawing, no matter the objective quality, tells me that you probably don't have a picture of the bike available to you in your mind.

Regarding your one eyed friend, the solution is pretty simple. Demonstrate what you can do with binocular vision that he cannot with ocular vision. I assume you could estimate distances better, throw more accurately, similarly describe three-d visuals as someone else, etc. If you couldn't actually do anything to differentiate your binocular vision from your friend's vision then I'd say he has a point.

Same argument applies to aphantasia. If phantasia people really do have a mind's eye, I'd expect them to have some ability that aphantasia people lack. As is, I doubt that it's a real phenomenon.

1 - https://www.booooooom.com/2016/05/09/bicycles-built-based-on...