I agree with the sentiment of mixing up sources. However there are not really many textbooks that rise to the level of "ground truth". Plenty of times that books give wrong explanations as well.
In my experience learning with llms is the equivalent of doing (bad) tutorials, and you end up in tutorial hell where you feel like you're learning but you find it hard to implement said thing without that guide. It creates surface understanding thats not really worth the effort. Its better to dive deep on your own.
We're all looking for that shortcut, myself included, but as the saying goes, "there's no free lunch".