I'm pretty sure speed reading is just reading without subvocalising which is a lot faster. Unless your brain also operates better at whatever your talking speed is the processing time shouldn't be any different.

I'm feeling a bit old thinking I need to look up this "speed learning" thing but I'm also already a little bit nervous about it just from the name O_O

lessons they should've learned and retained

Ahh the fun of reteaching people things they should know. It's even more fun when they claim they never got taught that to begin with xD I had some students who claimed that [previous coach] never told them to [do it this way], unfortunately for them I know [previous coach] and know for sure that [previous coach] absolutely would have taught them to [do it this way] because that's how [it] gets done.

My students at least have the excuse of being literal children. I don't know what your interns' excuses are.

they finished the chapters quickly and do chatgpt to pass through the assignments

Unless the assignment was on how to effectively use chatgpt to cheat help with assignments that you're obviously incapable of managing on your own thus negating any and all claims of "learning fast" that doesn't count.