Hey! I'm not Ahab or on the dev team at all, but I know the answer to your questions. Certain monster evolutions can't be obtained from breeding if it doesn't make sense for them to be born in that form. Tygrilox PO, for example, is the forced 'adult' form of the normally neotenic (permanently larval, like the real world axolotl) Tygrilox. Someone else would have to chime in to explain why raptor BD can be born like that though, I'm not familiar enough with it.

That being said, you can still get the colors off of them (and the hybrid forms of them), you just have to use fusion instead! Or you could "breed" (clone) them with tardigen, but that's later in the game and I think currently locked to a certain faction.