Ahh fair Zala. I must have missed that.
https://us.forums.blizzard.com/en/wow/t/torghast-highest-layer-now-unlocked-for-alts/850579
Based on this, you would only say need to do two level 8 on you main and then have it available to your alts. I.E they might not be unlocked retroactively but to do so it’s two runs at best.