The developers became worried and displeased after Apple has recently made changes to its guidelines. These changes concern apps for Apple Watch, and Apple directly declares that any apps for the watch which basic function is display of time will be rejected.
On the one hand, it is good that no one will ever spoil fine watch with a dial which Jonathan Ive would surely dislike. But, on the other hand, watch is an accessory which emphasizes individual style of the owner, and it would be great to allow the owner to choose the dial.
Apple limits us again, and we have to choose between 10 preinstalled dials, one of which is Mickey Mouse.