This is only accurate inasmuch as most salaried employees are overtime exempt for other reasons (e.g. because they are executive or administrative professionals). Paying employees a salary, on its own, does not make them overtime exempt.
One that comes to mind is an on-site caretaker position (e.g. on a remote property), where the employee is effectively being paid to be available, not to do a certain number of hours of work.
https://www.dol.gov/agencies/whd/fact-sheets/17a-overtime