TL;DR Yoda is not hiding the truth, but reassuring Luke that it really, truly doesn't matter, and that he (Luke) hasn't failed as fully as he thought he did.
I know this is pretty speculative at this time, but I've come to the revelation that Luke is only testing Rey's resolve every time he tells her that the Jedi must end, or that he went to Ach-To to die. This explains why he left a map and why
He becomes one with the force at the end (because he has found his replacement)
I think his petulance in trying to burn the books is the same impulsiveness he felt when
he considers murdering Kylo
I don't think he would have gone through with it.
His reluctance to burn the books is because he thinks he really has failed by pushing Rey too far (into leaving), and the books may yet be needed if he isn't around to teach the next Jedi hopeful who comes around.
Yoda reassures him that he hasn't actually failed, and that this is more like the time that Luke left his own training to save his friends. The parallels are all there, and Luke is just doing what Yoda did and said to him on Dagobah (from a certain point of view). The supposedly deleted scene of Rey's 3rd lesson from this answer here, indicates that Luke is just saying exactly what Yoda told him -- that it would be better to complete his training and possibly allow his friends to die, than to leave to face Vader before he was ready. While out-of-universe it may have been too harsh, I think including this scene would have made a lot more sense in the long run and would have gone a long way toward explaining a lot of what happens. In fact, while I guess that it was Mark Hamill's objection that may have removed the scene, I think the parallels it draws to Dagobah would have served to show that Luke was not the @#%#$! we see him to be, but that he just failed at being Yoda -- probably 'cause he ain't as cute as the little green muppet. Yoda was quite harsh with Luke, too, and nothing Luke did was beyond what Yoda did.
I think we're meant to realize that the same thing would happen if Rey were to return to Luke as happened when Luke returned to Dagobah.
("No more training do you require. Already know you, that which you need.")