"The earlier iPhones don't have the same NFC setup as the iPhones XS and later have. You can't even read NFC tags on earlier iPhones but you can on new ones."
Someone mentioned there's a chipset difference and ability to submit more power to the NFC chip on the XS, which perhaps makes more sense. But... NFC read/write ability in some form came with the 6S. There was a bit of hardware called Libre four years ago (NFC ISO 15693 -vicinity based, no tapping required) that could be slapped on your shoulder, scan the tag with an app to activate it, and pull data. That activation wrote to the NFC tag not allowing another device to subsequently activate it.