It does though, at least indirectly. If the point is to handle different screen sizes and resolutions properly that also has the side effect of handling window resizing; and if one doesn't work correctly the other will most likely have issues as well in some situations.

You can pick apart words and meanings as much as you want - a UI that stops fully functioning after the user makes a valid input I consider it broken. Hopefully you wouldn't call it "working as intended" either when a site becomes unscrollable, freezes up or literally moves sideways out of the browser's viewport when you type in a text field.

Resizing a window is not a weird edge case, it's been a basic UI feature for decades, supported even on some smartphones and tablets, and desktop applications have been able to handle it fine.