If websites had to ask permission to enable responsive features like screen size detection, then nobody would use them
My guess is the difference between "regular CSS that adapts to screen size" and "responsive CSS" is that the former only has a single set of rules while the latter has different CSS rules that get enabled/disabled based on screen size.
Conditional rules -> different content gets loaded -> server gets notified of what rules are enabled -> fingerprinting
Things went downhill once we started writing HTML which required knowing screen size ;-<