
no, he's not. it's actually the truth. go re-read chapter 0 (prologue), starting on pg. 57. the random man who says, "look what i found," is his dad. we see guwon bludgeon him to death.
it aligns with the update bc we get more context for it. what we thought was somebody who was trying to attack jinwoo, was actually his dad finding him water, but had his life ended by guwon.

This is just a theory so anything could still stand its just my take on it since we have two different sides and teach doesn't want to believe anything good about guwon so his brain could've changed the narrative
But you also have the figure who's supposedly his dad say "I'll make this a painless death" and before that going on about potentially looting the place that could either be guwon talking behind the father and jinwoo's head was so screwed up he couldnt differentiate the dialog
Teach definitely having his brain lie to him as a response to the trauma