The claim isn’t “Gazans lack permission to travel to Israel.” The fact is that Gazans cannot leave Gaza at all. They cannot travel by air because the IDF long ago destroyed the only airport in Gaza and controls Gaza’s airspace. They cannot travel by sea because the IDF patrols and has mined the coast, periodically murdering Palestinian fishers who stray too far from land. They cannot travel by land because the Israeli state has forbidden it and uses its control of Gaza’s borders to periodically murder any Palestinians who merely get close to the border.
Asking “isn’t this just like getting country b’s permission” is so fucking asinine. There’s no comparable situation in which the citizens of one country have to ask a second country for permission to travel to a third. Just vile shit that would be trivially obvious to you if you thought about it for even a moment.