Yes that’s correct, in order to unlock any of the Alliance allied races; you need to be Alliance and also meet the other requirements such as story quest line progressions and reputations for the required factions.
To further clarify, the guides was written based on Blizzard’s outlines for these races.
Dugiguides has all the guides needed to unlock all the allied races (legion or bfa) and if you do get lost along the way you can always ask questions in here.