We actually just see/feel/experience an explosion of colors/fractals but our perspectives and judgement, mold and organize the colors into a pattern called our reality and give it form.

perhaps

perhaps not

Many patterns are found repeated throughout nature that I swear blind I have seen similar to on journeys, both with DMT and other psychedelics to a (much) lesser extent in the past.

Trips me out that I was shown representations of the Fibonacci before I had any earthly idea of what it even was. Trips me out all the more to think that my brain was somehow showing this to me if I had no earthly idea (as per OP supposition).

Good things to ponder either way

People skeptical of the visions psychedelics give chock it up to, "oh, your brain is just making funny things, they're merely hallucinations and nothing more." As if to say, the visions are meaningless.

The visions are either inside my head, or from another source. If they are from inside my head only, that is really the more astounding explanation of the two, isn't it? My brain could that?

Our minds are as complex as the universe they inhabit. They have to be!

Things like the Fibonacci sequence seem to be founded in reality, which is why so many of us come across it in visionary states. Fractals in particular are so ubiquitous in Nature that it only makes sense that we experience stylized variations on fractal mathematics while in hyperspace. We aren't making this stuff up- merely recognizing and visualizing it.

I am not sure but i think the photoreceptor cells are arranged in an order representing an fibonacci pattern.
When you desynchronize your brain by altering your neurochemistry the actual structure of the visual processing gets visible. I don't think we visualize these pattern, its more like they disrupt through our 'normal' vision by superimposing on it like an wave interference.