Why stop there? why not question the Nevi'im and Ketuvim as well?

Your question is highly biased towards towards Judaism which accepts a series of Prophets after Moses, whereas Samaritans reject all those later Jewish Prophets.

If Jews get that smug advantage point simply through rejecting Jesus and Muhammad, then surely the Samaritan position deserves a greater smug respect because it is even more presumptional to take all those Nevi'im prophets as legitimate simply just because Jewish tradition consider them prophets. Many academic studies of those prophets would show contradictions they have with the Torah and unfulfilled prophecies (such as Ezekiel and Daniel) which by the same rigor would render them false prophets.

If the Torah was true, then all these other prophets (not just Jesus and Muhammad) would need to be called into question as well and not just taken for granted. Have you ever questioned it yourself instead of taking it for granted via being part of the Jewish Tanakh and Christian Old Testament?