Your "test iPhone" was not turned off, it just didn't have a network connection (because it has no SIM card). And yes, that has been a feature for a while – iPh

Your "test iPhone" was not turned off, it just didn't have a network connection (because it has no SIM card). And yes, that has been a feature for a while – iPhones without an internet connection can still be pinged via the Find My Network. The setting you see is about being "offline", not "power off", which are different things in this context. The new feature is iPhones being able to be pinged while the power is off. This is indeed an iOS 15 only feature, and also an iPhone 11+ feature, so it is certainly not available on your iPhone 7 running iOS 14.