Source: Discord

In Classic Cata they added a lot of mounts to bags you can buy from vendors as well as their normal drop locations

What bags/mounts? Presumably that's something that wasn't in Cata back then? Otherwise Rarity should already support it

No, it's a part of the new protocol dungeons they introduced in classic (Wrath and Cata) to assist in catch-up mechanics

Drop rates (taken from https://discord.com/channels/788119147740790854/1025387509741535374/1339180721591554100):

Stats out of 1493 satchels :

💎 Vitreous Stone Drake: 11 (0,74%)
🌩️ Drake of the North Wind: 11 (0,74%) 
👑 Drake of the South Wind: 10 (0,67%)

Total chance to contain a mount: 2.15%

Items:

• https://www.wowhead.com/cata/item=232947/satchel-of-the-cloudburst-cloak
• (what are the others?)

TBD: Presumably, the bags don't exist on Retail? If so, it might complicate things (more conditional logic? Not great)

This may require adding support for multiple sources per item if done "properly" (see #160).

Or, you know, we can always add more hacks.