As the industry slowly plods towards transitioning to USB-C - in Apple's case, at least in terms of laptops - tiny shifts like this are important as the port technology progressively becomes more popular.
But Apple is still frustratingly limiting the specification: unlike Lightning ports, which are also part of the MFi spec for accessories, USB-C ports can't be used for pass-through charging or syncing on iPhones. This means users still have to fork out upwards of $25 to grab themselves a USB-C to lightning cable.
Notably, Apple similarly started letting companies use its own Lightning port receptacle on MFi accessories a few years back and many Made-for-iPhone chargers, docks, game controllers and other products have adopted it since.
Apple's documentation for the new specs lists battery packs and speakers as products that could benefit from using a USB-C receptacle.
Though, adding a 3.5mm to Lightning, it's a useful addition for older headphones with removable cables or speakers with 3.5mm aux inputs. Whether or not this was a correct move is still up for debate, but regardless this has also resulted in an unfortunate spike in the need for dongles for users with headphones that still use the 3.5mm plug. If you want true fast charging on iPhone X and 8 devices, you're going to use the USB-C to Lighting cable.