First, I would say that it is accurate that Jews owned roughly 7% of the land in the British Mandate at the time the Mandate ended in 1948. That much is correct, or roughly so.

Second, I am not sure what "Ottoman citizen" status really has to do with it. The Ottoman Empire had completed its collapse long before 1948, and the British Mandate was ongoing. The Jews living there were not "foreign" in the sense that they did not live there, like some of the Arab owners of land in the Mandate (primarily wealthy Arabs living in places like Turkey). Indeed, more than half of the land Jews purchased in the 1930s was bought from landowners who did not live in the area, and lived abroad.

Third, there were not exactly "strong incentives" at the time for Palestinians to sell their land. In fact, the strong incentives were primarily that Jews were often willing to pay a premium for the lands, if the owners would just sell. At the same time, there were strong disincentives to sell, as selling would be viewed as taboo among Palestinian Arabs, even treasonous. Additionally, rules were imposed by the British in 1939 in their White Paper that restricted Jewish land purchases to certain areas and amounts.

Finally, this does not mean that the remainder was owned by Arabs in the area either. Instead, a good chunk (especially in the Negev desert) was owned by the state, and had been since the time of the Ottomans. That meant the land was owned by no one, and held essentially by the British during the course of the Mandate. Private land ownership for Arabs is a number I've struggled to find, if I'm being honest. I've seen claims that in the area Israel eventually was established in, i.e. the lines within the armistice lines of 1948, around 9% of the land was owned by Israeli Jews, about 16% was owned by Arabs who fled or were expelled during the war, 70% was state-owned land (primarily in the Negev), and the rest was owned by Israeli Arabs. However, this source is a bit suspect, it being a former Israeli diplomat, and I'm unfamiliar with other sources that break this information down fully; even the British, at times, appeared to allocate any state-owned land (which they themselves acknowledged was state-owned) to the Arabs when counting the land in their surveys, which has always confused me.