DakraMystic

Good video. I don't play tournament formats but kinda sorta keep up with news and this video was very good.

The model certainly has some obvious flaws like you noticed with Dynamo and Powerstone. I don't think it "counts" words or symbols on cards and it definitely doesn't have a notion of the "role" a card might play in a deck other than its key words.

I like using it when I have a card that has a niche intersection of mechanics/words and I want to find all the cards that are as similar as possible without manually searching every possible subset of those mechanics or words.

That's exactly correct. The similarity model basically ranks the importance of keywords based on how rare they are in the entire body of text. So for Counterspell "target" is pretty much irrelevant because so many things target but "counter" and "spell" are significant because they're rarer. Then it more or less quantifies the similarity of any two cards by how frequently they use these important keywords.