That's not true at all. An employer can demand that a salaried worker be in the office during particular hours. It just means that if those hours are > 40 per week, the worker doesn't get overtime.
Employers can "demand" a lot whether its justicable is another matter.
And a manager requiring attendance at say a 9 o'clock meeting is not the same as require you to be in the office 9-5 5 days a week