This is true for almost all Apple products though, and Apple has been rather successful at keeping the FCC report witheld until the product is announced. The most likely reason Apple is announcing this early is probably twofold:
1) It is a new product category, so they don't have to worry about cannibalization of the previous generation of the device. This is why they will never announce a new iPhone or iPad 3-6 months in advance. With a new product category however, they can build buzz, don't have to worry about part leaks stealing their thunder, and can get a better gauge on demand.
2) Freezing the market. Motorola/LG/Samsung all have announced and/or already sell wearables. By announcing the "iWatch" now, they effectively freeze the purchase of these competing devices - especially over the holiday period.