feeder3 works because Python's structural typing checks method return type covariance (accepting Dog as Animal), but incorrectly ignores parameter contravariance (should reject Dog input for Animal parameter). This is a type checker limitation (PyCharm/mypy may differ).

walker2 fails due to insufficient contravariance support in some type checkers. AnimalWalker (handles supertype Animal) should satisfy Walker[Dog] (needs subtype input) via contravariance, but PyCharm doesn't recognize

Behaviors are partially incorrect - true variance rules (per PEP 544) would reject feeder3 and accept walker2. PyCharm's checker has limitations in enforcing variance for protocols, unlike stricter tools like mypy.