It's a blanket policy—and it's a good one for you, your work, and your well-being.
You are killing yourself for for a job that would replace you within a week if you dropped dead. Take care of yourself. - Jet Li
That part about making things explicit is so important. I have avoided making sure things are clear with bosses in the past, based on a "we can work it out if things go weird" mentality and it has not worked out. Often fundamentally.