It's always been something that when you set the font in 1 server window, that changes the font for all server windows.

If you now do the same thing in any @window, clicking 'use default' doesn't actually set that window to forever use whatever is the default font. Instead, it defines that @window font font to be cloned settings to whatever the server window currently uses, and it won't change that @window font to mimic changes in the server window