If I'm an exempt (salary) employee, the company should have no say on how much of my time I put into doing the job they hired me to do, except to the extent it affects others (e.g. collaboration, meetings).

If they are happy with my results when I put in 15 hrs/week, they should just say thank you and pay me already, no questions asked. There is literally nothing to complain about.

If I can do the job from home in 15 hrs/week, and they still want me to sit in an office for 40 hrs a week, they should apologize for the inconvenience and pay ME extra for wasting 25 hrs/week of my personal time (plus commuting).
Many employee agreements try to give the employer a right to all of your "productive time". This makes no sense, is probably unenforceable anyway, and AFAIK has not done well in court.