I can't imagine trying to do that on an iPhone. Surely it's useless.
What this does do is reveal the fiction that "iPadOS" and "iOS" are separate. Clearly not.
Technically, I don’t think anybody ever claimed they were 100% distinct. Apple, for instance, says (https://developer.apple.com/ipados/get-started/): “Powered by the iOS SDK, your iPadOS apps”, and they’ve touted the ability to build apps that ru on both iPhone and iPad.
marketing-wise, they clearly are separate, in the same sense as https://en.wikipedia.org/wiki/Car_platform: “A car platform is a shared set of common design, engineering, and production efforts, as well as major components, over a number of outwardly distinct models and even types of cars, often from different, but somewhat related, marques.”
The only difference is that here, Apple apparently ships all or major parts of the special parts for the iPad on iOS, too. Maybe they also do that vice versa? Can you enable the calculator app on iPad with this method?