Grease should not be leaking (breaking down) on any brake system. Coming from dealing with car and motorcycle brake manufacturers. Engineers not sales.
Yeah it's normal apparently but I do mean from the bottle itself, not the pistons. I've had some spillages at home a few times and my deterrents have failed. It now sits very high on a shelf, and yes it still leaks.
Watch out. Hunters grease leaks like anything. Bought it for my Hope calipers, and every time I come back to it, more has leaked.
Top tip about using Castrol - I always try to find the source or automotive equivalents for this expensive rebadged bike stuff.