You are speculating without evidence. Handwriting may be more effective for memorization than typing because forming letters by hand is a more memorable act than typing, nothing to do with "choosing what's important to write". Since handwriting is so laborious, it leaves LESS time for thinking about what to write down, not more.

You can test this yourself by making a fair comparision:

* Copy entire documents by handwriting vs typing, with no regard to choosing "what's important", and test which strategy leads to better recall.

* Take notes from a lecture by handwriting vs typing, setting a goal of say 10% of the total material note-taken, choosing what's important to write down, and giving yourself as much time as needed to write or tye everything

* Similar comparisons, writing all vs writing selections, typing all vs typying selectionsl