It really was that specific. My wife’s phone was throttled and mine wasn’t. You could run a benchmark to find out until they updated the settings for more visibility.

My wife never did get her battery replaced - she was just happy with her phone as it was. If it randomly rebooted she wouldn’t have been happy and would have upgraded.

The feature still exists in iOS by the way, now it just tells you when it’s doing it and you can disable it if you prefer reboots. The feature kicks in when a brownout happens, that’s how its “targeted” at phones with degraded batteries.