simply using a LLM to condense an introduction from whatever data you feed it isn’t plagiarism.

Agreed. Though as you are saying, it is what you DO with it after that, which may make it plagiarism. A student using an LLM to personally learn? Not plagiarism. A student turning in that summary as evidence that they "understand" the subject matter? Especially without bothering to read it first? Now that is plagiarism!:-P

LLMs are tools like any other. Using a gun to kill someone? Well... is it self-defense? Then not murder. Are you a court-appointed executioner, in a state that offers the death penalty? Then not murder. Was it an accident? Then not... exactly murder. B/c you are Russia/Israel and you want the land next to you? Somehow also not "murder", depending on who you ask, but c'mon... really?!

Tools, by lowering the barrier to performing a task beyond what can be done naturally and unaided, mostly just enact the will of the user, though somewhat also act to "tempt" the user to do things that they might not have otherwise been able to do - e.g. murder, or plagiarize.

But congress-people did not need LLMs to pass bills written by lobbyists - the only thing changing there is how easy the latter process is, though to the congress-person it is the same level of ease as before, zero effort required:-P.