> universal theory of learning.

There is no such thing. Presumably there is a person who concentrates on algorithmic problems better while riding a unicycle. To the best of my knowledge the research shows people do not learn in the same way, although our hardware is more or less the same. The trick is to recognise what works for you, and only way to find it out is bu trying different things. Most people who succeed at all in higher education become experts on how they themselves learn best, simply because you won’t learn multivariable calculus, become fluent in Mandarin Chinese, or become an expert in late medieval poetry without trying every trick in the book to ram all that information into your brain.

Saying that, there is things that work for _most people_, active recall being probably the most universal one. Which simply means that if you do something a lot with a lot of repetition, you will eventually get quite good at it.And the probably is something in hand writing that forces you to actively engage with information processed better than typing for most/many people.

Personally, I have also noticed the better I get at touch typing the smaller this gap in enforcing learning by writing by had versus typing comes. That is purely anecdotal of course, but when we forced all the kids to use laptops to learn, did we teach them how to type properly first? Or to use computers in general? Or did we just gave them Chromebooks and said “good luck kiddo”?