Buffalo is quite right, the invention of a Palestinian identity was fueled by Arab political opposition to a Jewish state. There is no other reason they should not be considered a part of Jordan.
They should not be considered a part of Jordan for the same reason that England should not be considered a part of Scotland and Sweden should not be considered a part of Jordan.
Wherever I have traveled people gradually transition from one kind of people into the next kind of people. Austria was like Germany with a touch of Hungarian/Bulgarian/Serb/Greek/Turkish flavor mixed in. Traveling across India the ethnicities slowly change. Philadelphia is like a cross between New York and Baltimore. Palestinian cooking differs from Lebanese cooking.
Their is no such thing as a people without an identity. Writing suggests that most Palestinians looked Jerusalem as their cultural capital during the 1800s. I have no Idea to what degree the SanJaks were ethnic identities.
I still think of myself as a New Englander and a Bostonian despite having lived in California for 20 years now. When I go back to the Boston area the people there seem a little strange to me now but In California I can see the New Englander/Bostonian in me. Alabama feels more like a foreign country to me than Canada does.
Oakland, Walnut creek, Marin County, San Francisco, San Jose, Sacramento, Mariposa CA, Modesto, Fort Bragg CA, and Ukiah CA all feel very different From each other despite all being in Northern California. They each have their own cultures.
In my travels I noticed that older and poorer places have more distinct local regional differences than than than newer wealthier places like California do.
I have know enough Lebanese people and enough Palestinians to get a feel for the differences and similarities between them. I know nothing about Jordanians.I have seen nothing from the proponents of the Jordan is Palestine argument that suggests that they have given any consideration to who the Jordanians and Palestinians are. I don't know whether Israeli Jews know Jordanians. I don't think that many of the Palestine is Jordan proponents really care about anything other than protecting Israel when they suggest that Jordan is Palestine, therefore even if they saw a difference between Jordanians and Palestinians they would probably ignore what they saw.
I heard a story from an old man from Galilee who had to flee Galilee and who lived outside of the Middle East after 1948 and then moved to Hebron before 1967. He still lives in Hebron. He says Hebron is not Galilee and he is homesick for Galilee. He knows the Galilee that he grew up in is gone forever but Hebron will never substitute for Galilee because Hebron to him Hebron is physically and culturally not like Galilee.
On the other hand this America with it's internet and other changes is culturally not like the America that my mother grew up in and this causes her some discomfort.
Over all Jordan simply is not Palestine and it is absurd to say that it is just because of some lines that the British drew on a map before the British redrew the lines on the map.
If Israel backers want to be honest they should stick to what is real, like that Jews suffered during the holocaust and before the holocaust and deserved to be compensated if any body deserved to be compensated; like that being a minority has historically been dangerous for been dangerous for Jews and therefore they should be allowed to be a majority; like that Jews had as much right to conquer Israel as anybody had a right to conquer any other land;That Israel is the Israeli's home now and Israelis have as much right to not be driven from their homes as anybody else has to not be driven from their homes. Of course Israel backers should not be honest because this dishonesty probably is tactically superior to being honest.
But I am a fetishist for honesty which puts me in conflict with Israel backers.