However, traffic cops can check the documents of the driver’s companions, assuming they are wanted. But the simplest, as already mentioned, is the banal need to establish the identity of a particular citizen. Moreover, for committing such actions, the police officer is not obliged to inform the person about the reason for such need.
However, as a rule, traffic cops do not harass passengers from empty to empty. Usually, more attention arises for them when they behave inappropriately, are rude, swear, scandal, or exhibit a condition very similar to drug intoxication by their appearance. At worst, the driver himself was caught in the same drunkenness, in the passenger compartment of which substances may be prohibited for traffic. Passenger bags are no exception. True, the police have the right to search them only under video recording or with the involvement of witnesses. And people in uniform often check non-residents, which is actually not superfluous at all, certainly not in the period of the SVO.
In any case, it costs a law-abiding citizen nothing to show a passport to a police officer. If you are clean before the law, you have nothing to fear. But a dispute with the inspector can turn into a trip to the department, where you will not be “swept” without pleasure, breaking through the databases. Much worse when they get to the bottom of something else…