https://wccftech.com/apple-watch-series-7-does-not-have-a-hidden-diagnostic-port-might-use-wireless-data-transfer/

The Apple Watch Series 7 is finally here but it still has to reach the hands of the customers. Despite the bigger display, the Apple Watch Series 7 is pointing towards an 'S' year upgrade. This is due to the fact that the Series 7 does not change a whole lot when it comes to functionality but adds to the existing experience. If you remember, the Apple Watch featured a hidden Diagnostic port on the bottom. With the Apple Watch Series 7, Apple has eliminated the Diagnostic port. This means that the company will use wireless data transfer instead.

Located at the bottom band slot, the Diagnostic port is now gone with the Apple Watch Series 7 (via MacRumors). As its name suggests, Apple used the port for diagnostic purposes when the wearable came for service. For instance, it could be used to restore watchOS using a wired connection. If the Diagnostic port on the Apple Watch is gone with the Series 7, it means that Apple will now be making use of wireless data transfer. This explains the new 60.5Hz wireless data transfer module.