Freedom of movement != not showing documentation. (And it doesn't need to be a passport)

The simplest example is getting into any country you're a citizen of from abroad.

Some Schengen airports have security->passport (example AMS), some others have passport->security (example CDG T2), it's a non-issue.

Pretty much every country checks passports when you're leaving. The US doesn't as I pointed out in another comment, so they can charge you for a transit visa. (Some other countries allow sterile transit and don't check passports on exit - UK comes to mind - but you need a passport to travel to pretty much anywhere else from there)

> "temporary" controls that don't seem temporary at all

They have an end date. That's pretty much the definition of temporary. And yes there were previous temporary checks that have come and gone.

(If temporary checks weren't possible I guarantee how we would be reading about how the EU was undemocratic for not allowing member states to control their borders yada yada yada, the usual cynicism and uninformed rants that are so common here)