There is, but your example is not valid. You can't use short function syntax in constant expressions, it has to be an explicit `static function`.
The reason for this, IIRC (I can't find the GitHub issue or PR atm) is that these functions aren't allowed to close over any variables, and with fn syntax doing so is implicit. Rather than erroring they've disallowed the use of arrow functions entirely.
array_map(callback: fn($i) => $i * 2, array: [10])There are many very successful and professional PHP projects with millions of users that seem to be able to migrate to newer PHP versions just fine.
Whatever the WordPress developers are claiming are the reasons for their irresponsible codebase and their inability to improve it is nobody's fault but their own.