No, I don’t think so.
Trolls have had their overall culture (and accent) since Warcraft II. So it’s not a new thing that has cropped up since the launch of WoW. We’re going back to 1995, earlier if you take into consideration the development cycle of that game when they were creating these concepts.
This was concept art from Warcraft II:
So Trolls have always had a savage culture, long before Warcraft 3, long before World of Warcraft where folks tied the Darkspear Trolls to Caribbean culture. The seriously problematic staff that were outed in the lawsuit for being abusers and scumbags didn’t even work for Blizzard when these concepts were drawn up and used.
As for the Exploring Kalimdor book, that outrage was 100% manufactured, because as I’ve said multiple times on these forums, both in General Discussion and the Story forums, education is not widely available in the Warcraft universe. We have multiple examples of characters, both important and not, not knowing how to read, write or both. Thrall didn’t know how to read and write, neither did the prison guards who captured him after his escape from Durnholde.
The races of Azeroth, judging from the lore I can gather, have a mindset of ‘if it’s important to your job, then you’re educated on it’. So a Tauren loremaster/ambassador would know how to read and write Taurahe and Orcish, but a Brave who’s job it is to guard a town or patrol a trade-route probably doesn’t know how to read and write Taurahe and Orcish unless they taught themselves how to do it.
Now it’s true that Zekhan is an ambassador, but it’s really important to note that Zekhan was a no-name unimportant Troll until he befriended Saurfang and helped him in BFA. Before then he was your bog-standard Troll, which probably means he isn’t fluent in reading and writing Orcish, Thalassian or any language other than perhaps his own, and maybe not even that, because reading and writing aren’t key skills that a Shaman actually needs to perform their craft.
So the fact that he doesn’t know how to read and write doesn’t surprise me in the slightest, nor does it piss me off, and I say that as someone who has been fighting against racism and fighting for equal rights for indigenous peoples for over 20 years.