I'm really not trying to poo-poo the article but you could pluck 10 random things from Bootstrap's relatively simple documentation and have the same thing.
Maybe if it were titled "cool things in Bootstrap" instead of being presented as "tricks."
I'd call a trick something that is not part of the documentation core, something that has unexpected effect or behavior that was unintended initially.
None of those would apply here.
Either way, I didn't say such "tricks" are without peril - surely a number of jQuery "tricks," even those that were eventually canonized, have been broken over the years as the library updates.
If on the other hand you use a conventional definition of trick, "a clever or particular way of doing something", then the post is indeed about a set of tricks.