I was aphantasiac(?) most of my life and I self discovered similar techniques to what they discussed in the Reddit while learning multivariate calculus. I was trying so hard to visualize the integrations and using the “fuzz” I see when I close my eyes to infer the shapes then one day I could actually see them in my minds eye. I never applied the technique to other things because I didn’t have the same motivation to practice that induced my first breakthrough but I am pretty confident the technique works. The plasticity of the brain is remarkable and it’ll adapt to what you need it to do if you work at it.