In Microsoft's input method, shift will toggle you between ascii input and pinyin input while not switching you out of the pinyin input method environment.
I tend to use win+space, which instead toggles the input method you're using, as opposed to toggling how the pinyin input method interprets your input. But I had to learn about this secret special functionality of shift, because (some time ago; I don't know if it's still true) after switching your input method with world of warcraft running, the chat UI in the game would become nonresponsive.
After all, who ever heard of wanting to switch between different languages while using a chat interface?
Interesting, that’s perhaps where the idea came from then. What I witnessed was actually on a MacBook Air running macOS maybe 10-12 years ago, probably a version of macOS before they really improved the native pinyin input. The person had installed a third party input method (icon was an S is all I recall) / manager which changed by default how the shift key worked as you describe, it’d keep using that input method but it’d be in English mode.
I recall thinking shift was an insane default but it did explain why she used CAPS LOCK to capitalize single characters.
I tend to use win+space, which instead toggles the input method you're using, as opposed to toggling how the pinyin input method interprets your input. But I had to learn about this secret special functionality of shift, because (some time ago; I don't know if it's still true) after switching your input method with world of warcraft running, the chat UI in the game would become nonresponsive.
After all, who ever heard of wanting to switch between different languages while using a chat interface?