Piracy protection is things like encryption, firmware checks, pairing systems, unique game identifiers per instance of game, unique console id’s, … Basically any system put in place to make, or identify, a game/console to be genuine or make sure a genuine game running on genuine hardware and nothing else.
These are all systems the switch had btw.
Switch emulation bypassed or faked all of those, which counts as piracy protection circumvention.