Correct, because they do two different things. `which` is a standalone executable which searches the environment's PATH for the named command. It doesn't know

Correct, because they do two different things. `which` is a standalone executable which searches the environment's PATH for the named command. It doesn't know about commands which aren't executables (i.e. builtins and aliases). `command` is a shell builtin which tells you exactly what that shell in its current state would run.