If you are interested in this topic, the author of pooltool[1], a billiards simulator, has a nice blog series about it [2].
This material deals with spin, unlike the article.
It also has illustrations, unlike the article.
And here is a video of a robot playing pool:
Unfortunately, this writeup doesn't mention any words like "spin" or "rotation" or "angular", not even to disclaim that those aspects are not presently being addressed. It looks like a great resource for kids in grade 11 or 12 physics.
Since it also doesn't mention friction I'm a bit confused what effect, if any, you were expecting to see.
Dealing with friction complicates matters significantly. At the very least you can't expect the collision to be elastic.
The intended audience is the author himself.
Edit: You’re reading his notes/summary of the topic. Basically what he’s understood so far. “Expository webpages - For my own future reference. Intended audience is myself.”, see https://vanhunteradams.com/#Expository-webpages
Chances are the author is in 11th or 12th grade. And you two might be on the same page.
(Just joking).
A very nice article. I noticed a small typo: "resitution".
While rare events, it would be lovely if this also included notes on how to deal with "more than two balls" simultaneous contact cases.