The idea with SRS is that the exponential scheduling is supposed to be more efficient than random or sequential scheduling.

I did study for medical exams with mnemonic techniques. Studies have shown that they do not inhibit understanding at all. In my experience they even help understanding. They totally dominate SRS on anything looking like a table or list. With text it's not as pronounced, but still you can memorize the key words, as few as possible, as many as necessary.

Flashcards are first of all a rewrite of the original material. If that is really necessary, the original material sucks, at least for the purposes of the exam. The physical cards are marginally easier to use than a textbook, but then again, writing them takes a lot of time and effort.

SRS is mostly about the learning schedule, i.e. equal intervals and increasing intervals.

How you execute, whether with mnemonics or flashcards, is different.

With the umbrella term of "study or learning techniques", the learning schedule and execution are both included.

Usually when people talk about SRS, they mean flashcards or Software. At the very least you would need to keep track of the learning schedule and what you forget. Which I found impractical for learning large amounts of stuff.