Your brain is much more susceptible to damage, and inaccuracies than other physical items. Our memory as humans is absolutely awful, and that's even at the beginning of our life spans, though as we age the brain, and therefore the memory also deteriorates along with it, this is without including the possibility of brain diseases which can effect your memory.

This memorization technique is fun, and although it might be suitable for certain people, I wouldn't count on my memory even if I did. I've also practiced the memorization techniques of loci, and while I might have thought or even used it with a Bitcoin private key, I certainly wouldn't rely on it as a single point of failure. I actually got into the technique via Derren Brown, who's an expert of misdirection or mentalist if you'd prefer.  He uses this technique multiple times in his shows, one show he uses it to memorise a large part of London streets, and it almost works flawlessly on the night.

However, I couldn't with good conscious while openly admitting this technique is actually quite effective, recommend using this as a single point of failure to memorize a private key. What do I mean by single point of failure? Well, I mean this shouldn't be the only way that you are remembering your private key, seed or whatever. Contingency plans are needed for everything, in fact I think you should have plans for a system that includes as many systems for point of remembrance, without compromising security, especially if you're holding onto anything of considerable value.