You’re right, calling all the released prisoners “Palestinians combatants” would be wrong. Can you please point me to a source calling them that? I only saw something similar in far right Israeli news sites, who call them “terrorists” (all other sites call them “prisoners”).
Yes, all of these people are charged by the Israeli state, an apartheid state oppressing the Palestinian people. They can make up whatever charges they want. Who believes them?
If we assume a state-wide conspiracy, any state can make up whatever charges it wants. There’s no real way to prove that’s wrong. However, there are a few indicators I can think of - what’s the democracy index of said state? is that state’s judiciary system regarded internationally as being generally good? Do other democratic states believe said state? Has said state been caught in many lies regarding its judiciary system?
Going by these indicators, Israel’s status is at least OK. Not perfect, and if you’d like I can point out quite a few issues, especially regarding the treatment of Palestinians, but they do not “make up” charges as a general modus operandi.