It’s too convoluted for alts to unlock BFA content.
It’s odd there is no skip for Ny’alotha, otherwise everything is unlocked super quick though
No you still need to do the intro quests for Boralus or Zandalar, then do the HOA quests to unlock the HOA and your first essences, then unlock Nazjatar, then do the 8.3 intro stuff and only then can you do any of the content in BFA.
You want to do Legion? Click the skip button. How about SL? Skip. TWW? Skip.
You can skip the Boralus intro, and the Heart of Azeroth is 2 quests.
I couldn’t, and I’ve done Boralus and Zanadalar on alts before, but still had no skip quest.
I so far have done the first and second HOA quest, including going to Highmountain, now I am doing the 3 foothold quests to hopefully unlock the Uniting the Isles quest, then I might need to do Nazjatar and Mechagon on top of that before I can start the 8.3 stuff.
Not sure if this is what you are looking for, but the only skip i know of is to pickup the quest from chromie time, portal to blasted lands, abandon quest, go through portal.
You should now be where you walk to your garrison.
How does this help with Battle for Azeroth (BFA)?
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I recently experienced what Akapally did. No skip over the intros to BFA. Ended up dumping the expac and going to Legion.
Please pardon my lack of reading comprehension 
Problem is for mount hunters there are a good number of mounts, and if you want to farm N’zoth now with the account wide raid skips you need to go through ALL that to unlock Ny’alotha.
Was it undone? I just asked Nathanos to skip the intro and go to Zuldazar (Horde).
It’s pretty annoying but it doesn’t take all that long to get alts into the assault stuff. You can skip the BFA intro quests but can’t start the Nazjatar chain till level 50. Once you’ve done the Nazjatar chain once you only have to complete up to “Welcome to Nazjatar” part of the achievement for your alts to be able to accept “An Unwelcome Advisor” from the Missive on the table in Boralus.
I started a new character last night, and he’s getting his cloak right now after working on his class hall and running some dungeons. It’s that quick.
The Highmountain quest is part of opening Nazjatar. Uniting the Isles is automatically available at level 50.
Wasn’t for me. I had to get the first HOA stuff, then do the first couple of quests for the three zones, then because I also want 8.3 stuff unlocked I had to do the second HOA stuff and then some before I could get Uldum and the MoP zone opened up.
Because you need the HOA and cloak you need to do a few hours worth of questing in BFA still. Quick is the Legion, DF and TWW skips were it literally skips you into the new zones with everything unlocked.
I also tried SL last night and forgot they took that skip out, so now if you want SL you have to do basically all the OG zone questing, so no more alts into SL sadly unless you are an engineer and can port into some zones with restrictions.
because you’ll probably end up in the ocean somewhere