That's great, however my current employer said on day one that they expect my timesheet to be 100% billable hours and the categories within our tracking software are designed specifically to a limited set of other categories (that could be defined as "bare minimum responsibilities that a professional has that could be considered non-billable".)

The point of this is to make you believe that non-billable downtime is a punishable offense. And a sort of brainwashing that if you are experiencing downtime, there must be something horribly wrong and you are failing to ask for more work, not communicating with your manager, etc.

So to summarize, in my field, being "exempt" does nothing more than to add additional stress since employers are allowed to frame the implicit, expected nature of "exempt" work as a horrible evil fault of the employee. And, if my feelings are correct, trying to apply time to my timesheet as "non-billable" is a fireable offense.

Hopefully I'm making the case to you that "at-will" employment cannot co-exist with "exempt" employment. By agreeing to work "at-will", employees undermine their status as "exempt."

Or, on the flipside, it teaches all the labor force to become good liars.