Secure action buttons OnReceiveDrag and mounts

[Duugu]

I'm experiencing some strange behavior with my custom action buttons (derived from SecureActionButtonTemplate and ActionButtonTemplate) when dragging a mount from the Pet Journal list onto my action button. The resulting arguments in OnReceiveDrag are somewhat ... strange.

Dragging the first mount ("Albino Drake") onto my action button passes the arguments 0, Mount, 268 (kind, value, subtype) to OnReceiveDrag. The first two are as expected. But what the hell is 268? Shouldn't this be 1?
No surprise: /script C_MountJournal.Pickup(268) does not pick up list item 1 (Albino Drake) but item 268 (Mottled Red Raptor ... or whatever it is in your list).

Same problem with any mount that is dragged from a default action button onto my custom button.

Is someone able to confirm or disapprove this problem?

Or do I have to do something with 268 to get the actual list item? Filtering or something?