Are they descendants of the Jews who stayed in the middle east during the Diaspora but were arabized and lost their Jewish culture and became culturally/ethnically arab, or are they arab descendants from when Palestine was controlled by Arabs like the Caliphates and Ottomans. I think Sephardic and Mizrahi Jews are Hebrew descendants who didnt mix too much with Europeans like the Ashkenazi did, which is why they look more middle eastern, and they look similar to Palestinians (Palestinians arent as dark as gulf arabs), but that doesnt prove that the Palestinians are actually hebrew descendants.
Probebly some are but if you ask them they will deny it, they call themselves Arabs and have family names to prove it : El Masri - Egyptian, Zoabi - Iraq, El Azad - Yemen and so on......