Is it really normal, that german police when stopping car, because of passenger not wearing seat belt, is checking passenger's ID and not driver's?

Never heard about this procedure, at least in my country, driver is responsible for passengers and only checked person in car (of course not on border and if police has some suspicion about drugs/weapons/organized crime), when is his passenger not wearing seat belt, driver just pay fine and that's all (if he then takes money from passenger is their problem), but never heard that police would check passenger's ID instead driver's one.

So when police stopped their car and said she is not wearing seat belt I though it's just routine control with usual fine and it's just to scare viewer, but when police asked for Ayten's ID I was totally surprised because I find it totally strange to ask ID from passenger who is not wearing seat belt.

If this woudn't happen, she wouldn't deported and she woudln't go to jail and german GF wouldn't go to Turkey to get killed, so I find is as huge flaw, at least they could try different way how to show checking of her ID (like they are in club and police goes there because of drugs and checks ID of all visitors, this would look definitely much more real to me than checking ID of passenger (not driver) because of seat belt, I find it totally unrealistic).