There are a handful of pvp talents that "require" a level far below when theyre actually accessible. No idea why.
Yeah, it says that for BfA as well. It's the spell you get by picking the Heart of the Wild PvP talent—first available in the 40s.
1) It might be just Blizzard throwing random level numbers, maybe because their internal systems require some number to be put and the devs just want to be quick with it. No problems, because the real requirement and its intended level are perfectly sorted out.
While I agree that's not redable for the outside observer nor elegant when you see the clockworks behind, I guess it's most likely irrelevant. There are some strange behaviors (ex. Portal to Old Dalaran being accessible to party sync'ed mages at lower levels than it is obtainable), but the main problem is that some things can only be reliably tested in-game.
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2) Additionally, the unusual level requirement might be a smart design trick for better player experience in some way.
For instance,
https://www.wowhead.com/spell=175682/natures-control is a hidden druid spell learned at lvl 1 that is replaced by their lvl 60 talents. The trick is, since the talents replace Nature's Control rather than giving new skills, the player can make a single macro for all of the different spells by typing only /cast Nature's Control.
And since Nature's Control is lvl 1 spell, if Blizzard needs to switch the lvl 60 talent row with the lvl 45 for Feral only, it should still work for all specs. No new changes are needed and time is saved.
But I digress, more Alpha answers soon.