Peer Rec Issue?

Ok so I asked my friend to write me a peer rec for Dartmouth and I believe he submitted it sometime around last week. He assured me that he wrote a good letter but then he recently proceeded to talk about how he mentioned why I would be a good fit for Dartmouth. Essentially, he tailored the rec letter to the school. Now from what I’ve heard, this isn’t necessarily a bad thing but it isn’t a good thing either because according to some of my other friends, tailoring a rec to a specific school isn’t allowed? Are they right? How will this affect my application given that, according to him, the overall letter is still pretty strong? Furthermore, I do not intend to submit this letter to any other school besides Dartmouth if that matters.

I admit this may be a stupid question but it was just pestering for some time. Any help would be appreciated. Thank you!