That is incorrect. That "key difference" is not even remotely a universal truth.

I've been a consultant and an employee many times in my career. You can take any variation of the following sentence and it'll remain true:

I've worked for a company as a [ hourly consultant | salaried employee | per project consultant ] that [ monitored my every keystroke | monitored attendance | monitored nothing ].

Every variation is possible, and I've seen every variation.