I completed this today, but didn’t get the reward which is a Pale Regal Cervid. Immediately after I got the achievement, I got mail. The mail said, basically “We discovered this item in one of our vaults. Apparently it belongs to you.” But there was nothing attached. Just a letter.
I was about to submit a ticket but decided to visit the protoform synthesis mount NPC up north (Kodah) figuring it may have automatically been added. Turns out, I had the schematic already. I earned it yesterday before I got the achievement. I’m certain of it because I had two schematics learned yesterday and going back to look today, one of those two is the Pale Regal Cervid.
So there’s really no reward for this achievement.