(But yes, it will still work if you have a mac WoW folder)
You do not need to download a mac 2.4.3 WoW folder, since it’s faster to just dl a windows 2.4.3 and put the World of Warcraft.app inside it and run it. To install, just put the World of Warcraft.app into your 2.4.3 TBC folder and hit replace. Note that some servers such as Warmane block the native MacOS client.
u/vanillalad over on reddit figured out how to get the native Mac client working. WORLD OF WARCRAFT AND BLIZZARD ENTERTAINMENT ARE TRADEMARKS OR REGISTERED.