according to the internet, I'm a Gen-Z myself, and I don't think this is true at all. I know like 3 people who upgraded to Big Sur because they liked the design. But everyone else stayed on Catalina, because they either heard horror stories about macOS 11, or, like me, had awful experiences with it. I upgraded my main machine to Big Sur three times, and always reverted back to Catalina (even downgraded my MacBook from sur to Mojave after a few months).iOS 15 was not popular, iOS 13 was not popular. The reason was because there was no customization. Almost every gen-z updated to Big Sur since they liked the redesign.
In fact, most Gen-Z "kids" I know don't even bother with updating their devices.