From the linked page:
> The ability to index expressions was added to SQLite with version 3.9.0 (2015-10-14).
So this is a relatively new addition to SQLite.
i initially misread "2015" as "2025", too... But no, it was part of SQLite for ten years already!
I'm not sure 2015 counts as new, but that's same release that first introduced the JSON extension. There isn't a version of SQLite with JSON expressions but without indexes on expressions. Also, the JSON extension wasn't enabled by default until 2022, so most people using SQLite with JSON have got a version much newer than 2015.