I think the difference is that pandaren are a neutral race and were bringing in an entirely new class as they came. While I wouldn’t mind some diverging in how monks are done, I know it’s way too late for that.
Another problem is that this isn’t the first time alliance themes were being pressed on the horde. All of druid, for example; first with tauren to prevent one faction from having two unique classes, but then again with trolls in Cataclysm as everyone got folded into the Cenarion Circle. And arguably yet again in Dragonflight, since for some reason Wardruid Loti of Zandalar is responding to the call to defend the Emerald Dream alongside the other CC members.
There was also a line that got cut in the Legion beta about Aponi Brightmane being helped to learn “the truth of the light” or something like that in the paladin order hall. And to be fair on the alliance side, it does happen with a night elf who chooses to abandon being a priestess of Elune in favor of training to be a paladin, which wasn’t well-received. Then again with mages as we see orcs and vulpera in Dalaran attire.
I don’t think we ever see this happening the other way from the horde, though. No alliance races being written about wanting to adopt horde practices or beliefs. And the class halls lean harder toward being alliance-themed to begin with so there’s really nothing the horde has to offer, if players would even want that.
Honestly, after BFA, I think alliance fans would likely revolt at the idea of night elves or worgen learning shamanism from the horde over dwarves and Kul’tirans.