The Golden Clock is more about debris so it doesn't stop Grass from randomly growing on your Farm, though it does stop random Trees from starting to grow. It's kinda arbitrary as you'd think it was either Trees + Grass or neither. The only reason I can think for it to work like this is a good one:
This allows you to plant Grass Starter on Winter 28 and still get the GrassExplosion on Spring 1 to completely refill your FarMeadow with Grass for your starving Animals. Strategy is very important to the Lazy Farmer.