FWIW, my print screen button does exactly the same thing, literally; it's opening the snipping tool in "select a region to screenshot" mode.

This is a setting in Snipping Tool (called "Use the Print screen key to open Snipping Tool").

When I encounter this bug, Win-Shift-S behaves identically (i.e. doesn't work).

Especially since it can open with selecting the area to screenshot and not have to manually crop it in Paint or be sending a 4K image to someone.