Media queries have been based on "effective pixels" rather than actual screen size since early in iOS/WebKit development and entrenched (or worsened depending on your perspective, I suppose) in the "retina" shift and other browsers following suit. It's a communal hack, but you can mostly assume that a modern browser is going to choose applicable media queries based on what it best thinks its pixel density and device form factor may be, rather than actual specific screen size. (Including things like Windows' Tablet Mode switch signalling to Edge to apply media queries differently.)

It might have been nice if CSS had more standard media queries that stated more explicitly what is desired (@media tablet-screen {} or something similar), but the compromise that remains is a solid one that mostly works and is adaptable/evolvable to potential future shifts in device profiles (both in browsers choosing different "effective pixel" ratings over time on the one side and CSS writers shifting breakpoints on the other).

Yes, new CSS standards like Grid/Flexbox could try to invent new wheels to deal with responsive issues, but it's easier for those standards to get adopted if they just subsume existing standards such as media queries.

I'm curious how you manage to avoid media queries while building "truly responsive" websites.