very reasonable

Have you asked them if they can just pay it out? It might mess with their budgeting slightly, but they'd be paying the same per hour worked so likely not be a big deal.

it's more i wish we had a culture of encouraging people to take more time off, where it was normal/expected. (actually, i think the ideal way to work for me might be something like "insane hours for 3 months, no work for 3 months". or maybe every two weeks. or something.)

i just think there's a strong expectation/cultural momentum to be working all the time, more than is healthy. you can swim against it, but you're still swimming against it.