OP, how many of the 100 deliberate errors in the Williams’ link did you spot casually? Is this paper well known in linguistic circles? It is none too kind about Strunk, Fowler and Orwell who have been attacked at wordorigins often.
In my youth adults would get on our cases for using can when they thought we should use may. One of the little things that I believe foreshadowed my interest in words and language. I noticed that they themselves generally used can in the very context they were at us about. The only time I heard it used the way they thought it should be used was in the game we called “Mother may i?”.
When a teacher at my benighted school was asked “Can I go to the the toilet, sir?” he would reply “I’m sure you can. The question is whether you may.” How we laughed. I used to have to ask my parents “Please may I leave the table?” - received manners. What do kids now say? “I’m done here. Splitsville?”