Confirming previous datamining, the Dread Hatchling does indeed have a brief heart animation over its head when you mount up on either the original Raven Lord mount or the new Dread Raven.
Each time I see this, I imagine it chirping, "Are you my mommy/daddy?" :P
The Dread Hatchling is currently cageable, however, this is a bug that will be fixed soon. There are also reports that relogging after caging will result in a new pet in the mail.
I'm not sure how Blizzard will resolve this issue after fixing the bug. There are already mentions that the hatchling is popping up in Auction Houses on multiple servers. Will all cloned hatchlings be removed from the game? Will players that sold their pet receive an infraction on their account? Will they be able to re-acquire the pet or will it be gone for them forever?
In any case, it's not advised that you cage and sell/trade your hatchling. It's unclear what the consequences of doing so will be. You could lose your hatchling completely. :(
All I can say is that out of respect for the game and for the developers, keep your Dread Hatchling safe and sound in your Pet Journal.
Edit: Apparently if you purchase a caged Dread Hatchling without having already purchased the CE or Digital Deluxe, you cannot use the pet. This is a good solution for all of the duplicate hatchlings without having to manually go through and delete them.