Also, the PLO had no qualms with making territorial claims to the whole of the Mandate, including all of Jordan. So this notion that Jordan is somehow separate is news to the Palestinians.
"Then why did Palestinians join with the British to fight the Ottomans during the First World War?"
That had nothing to do with Palestinian nationalism. They wanted an Arab state encompassing the whole of Ottoman Arabia. Show me where there was any notion of Palestinian nationalism during WWI. No, they all followed King Faisal's idea of Greater Syria.
"And then why did they rebel against the British in the 1930's?"
It's called the 'Arab Revolt' and the 'Palestinian Revolt' for a reason.
Why did the Auni Bey Abdul-Hadi tell the Peel Commission that 'Palestine' was a 'Zionist invention'? Why then did the PLO as late as the 1970s claim that the 'Palestinian people did not exist'?
"“The Palestinian people does not exist. The creation of a Palestinian state is only a means for continuing our struggle against the state of Israel for our Arab unity…Only for political and tactical reasons do we speak today about the existence of a Palestinian people, since Arab national interests demand that we posit the existence of a distinct Palestinian people to oppose Zionism. For tactical reasons, Jordan, which is a sovereign state with defined borders, cannot raise claims to Haifa and Jaffa, while as a Palestinian, I can undoubtedly demand Haifa, Jaffa, Beer-Sheva and Jerusalem.”"