Misleading on your part. From the US Dept of State:
"The population of Transjordan before the war was about 340,000. As a result of the war, about 500,000 Palestinian Arabs took refuge in Transjordan or in the West Bank. Most of these people had to be accommodated in refugee camps, which were administered under the auspices of the United Nations Relief and Works Agency (UNRWA) for Palestine Refugees in the Near East, set up in 1949. In addition there were about 500,000 indigenous residents of the West Bank."
Jordan certainly holds large numbers of Palestinians - but it is home to Bedouins as well, and they are not the same, despite having similar religious roots (92% of Jordanians are Sunni Muslims). One consequence of this fundamental difference was King Hussein's moving against the PLO and driving it out of Jordan when he sensed a coup was near.
Jordan, incidentally, follows a mix of Islamic law and French code, in contrast to other post WWII "carve-outs" which followed the British way...
Equating Jordanians with Palestinians is the same sort of simplification that lumps most African-Americans together, regardless of where in Africa they came from.