Please note that Peter equates Paul's writings to Scriptures. As some have tried to make a case that Paul's instruction to Timothy was in regards to the Old Testament; presumably Peter is equating Paul's writings to the Old Testament scriptures.
But Peter is not making a comparison between the merits of certain books; his statement is that some people distort both. One can say that the comparison implied in "also the rest of" is not intentional. If I say "first-graders do not understand Shakespeare as they also don't understand chemistry" I assert no equivalence between Shakespeare and chemistry.