> Isn't it considered Jordanian land, since they annexed it after 1948?

The Jordanians occupied the land, and the annexation was recognized by only two States (Iraq, ruled by the Jordanian king's brother, and I forgot the other one). The Arabs now disregard that annexation, under fear that it would legitimize an Israeli annexation.

Everything in this conflict is a war of words and changing one's interpretation of past events to suit current goals.