The 30W USB-C Power Adapter that's replacing the 29W version is designed for the 12-inch MacBook. It's also commonly used as an option for those who want faster charging for compatible iPhones and iPads that support fast USB-C charging speeds.
It is not clear why Apple replaced the 29W Power Adapter with the new 30W Power Adapter, but the pricing remains the same at $49. The new accessory is not yet in Apple Stores, but can be ordered today for Wednesday delivery.
Apple has not tweaked its other USB-C Power Adapters designed for the MacBook Pro lineup, with those accessories continuing to be available in 61W and 87W options for 13 and 15-inch MacBook Pro models, respectively.