It’s extremely common to support the two most recent major versions, especially for iOS. It’s great if things work on iOS 14, but it’s been explicitly out of support for over a year in a vast number of organisations.
It just barely supports Safari 15, on iOS only, and that’s likely to go away imminently because it’s under 1% usage.
Browserslist is used by a huge proportion of web developers and the tools that they use, with millions of downloads a week. It has nothing to do with native apps and everything to do with the web.
The issue here is the version of the webkit engine, which ships with iOS and that is 3 years old. Anyway a docs page is basic, it should be compatible regardless.