minimumButton and maximumButton props for Window are weird (?)

Hi Team, 

How do I use the min/max button props for windows? Im trying to hide the buttons without success, I've tried these values with the following results:
true/false - failed
"true"/"false" - works, but theres a warning in the browser console. (If it doesnt appear at first, refresh the page)
blank string - failed
the letter 's' - works, no errors (this was an accident, some letters work, some dont. I didnt try them all)

StackBlitz Demo

Thanks,
Grant