Do you mean the short-term memory needed to apply the commutators or the conjugates? Otherwise you only really need to "memorize" the steps of the method.
I learned this method around 10 years ago, and I can still solve the cube without applying any memorized algorithms because of it. It really is the only fun way for me to solve the cube after all this time.
This. I used to forget the algos whenever I didn't touch the cube for 6 months. Then learnt Ryan's method. Picked up the cube 4 months later and found I can still solve it.
I learned this method around 10 years ago, and I can still solve the cube without applying any memorized algorithms because of it. It really is the only fun way for me to solve the cube after all this time.