This doesn't appear to be a bug, just a mistake, but i'm reporting it anyway just in case.

Basically, whenever a Crocodile or Terrapin Egg is broken without Silk Touch, they drop themselves, but what's weird is that Turtle Eggs don't drop themselves if broken unless Silk Touch is used which means the Crocodile and Terrapin Eggs shouldn't drop themselves if no Silk Touch is used. The Caiman Eggs don't drop without Silk Touch so I'm not sure why the Crocodile and Terrapin Eggs are exempt.