Currently, if you're a human, you learn "Horse Riding" from Randal Hunter in Elwynn Forest. It's the only thing he teaches for 16g with my discount. This "Horse Riding" allows you to ride blue/slow or swift/purple mounts. There is no 75/150 listed in the Skill pane. The mounts claim to need (1).
In TBC there is 75/150/225/300 riding skill, and from the faction trainers, there is no "Horse Riding" or "Mechanostrider Piloting" as it's replaced with "Apprentice Riding" and "Journeyman Riding" with Expert and Artisan being flying.
Do we need to own a Swift mount in order to auto-learn Journeyman Riding during TBC transition? What about Warlocks who don't have the Dreadsteed? Players in Classic WoW had their skill increased from 75 to 150 upon earning their Dreadsteed, but there aren't such numerical skills on the Onyxia server. It was considered an economic investment to spend 150+ gold on the Dreadsteed to avoid the Journeyman Riding cost, but with Horse/Wolf/Tiger/Ram Riding, you already gain access to Swift mounts.