Do you have any reasons for this beyond ease of reproducing portions of the text to drill yourself to remember it verbatim?
But, more to the point: You seem confused as to the true generality of the technique. Flashcards can be used in much more interesting ways than just checking to see if you can recite all the lines of Homer correctly or something.
The vast majority of cards I have are questions of understanding - e.g. a card like "How many unique strands of DNA can be made from 100 A-T pairs and 100 C-G pairs?" You can't memorize all those digits. You need to remember how to solve the problem, which is quite simple, but not so simple it's worthless for a non-mathematician to solve without pen and paper.
The question side of the card may be directly copied from the textbook, and read something like "An increase in the supply of a complementary good Y typically causes the price of good X to [...]." You can then correctly answer "decrease" or "lower" or "go down". You don't need exact phrasing, because you are grading the card yourself; and actually forming the cloze deletion is in most SRS programs a single keyboard shortcut away. This 10 second loop of copy, cloze delete, create gets you a huge amount of the benefit of learning and remembering the reasoning embedded within the sentence. Imagine trying to create a cloze deletion by hand - you'll be there for 2 minutes just copying the sentence.
The next level up is an image occlusion, where you actually screenshot an entire diagram, math equation, section of code, etc. and then selectively hide parts of it, asking yourself to fill in the blank. https://ankiweb.net/shared/info/1374772155
Image occlusions are close to trivial in a program like Anki once you've made a few. But they are, for all intents and purposes, impossible to make flashcards of unless you feel like drawing e.g. an anatomically correct human brain the same way 17 times in a row.