No, iPhones released as of today, March 4, 2024, haven't had reverse wireless charging. It's possible that the device you bought underwent some hardware changes by the previous owner, and you might not be aware of them.
There is no information in Apple articles supporting the idea that the iPhone 8 has wireless charging capabilities to charge another phone using the back of your iPhone 8.
I have been using my devices ever since I bought my first device in 2009. iPhone 3Gs, 4S, 5, 6, SE (1st Gen), 7, 8 and iPhone 12 Pro, iPad Pro, iPhone 13, Macbook Air 2019, MacBook Pro 16"
I still have SE (1st Gen), 8 and iPhone 12 Pro, iPad Pro, iPhone 13, and MacBook Pro 16".
None of them have this feature
