Hello,
I encountered a real big issue when developed a modal window on a site, in which height is 100vh with a ‘confirm’ button at he very bottom.
In emulation responsive mode no problem at all, but… in real devices, browsers like Safari and also new Firefox mobile have an address bar or status bar the cover this button.
Unfortunately 100 vh are not calculated onto real available space but simply ignore presence of these kind of bars.
A great help could be the possibility to have fake bars also in “Responsive mode”