Yeah I agree. I think "The Devil in the Dark" made it pretty clear that was our first encounter with the Horta. There was nothing there to indicate otherwise. Dr. McCoy thought it was fantasy for their to be a silicone based life form. And it seemed the miners never encountered anything like the Horta previously.
And I agree also the 'lost records' trope, and classifying things, and some of the others they have been using to justify things is starting to wear thin. SNW is my favorite of the Kurtzman shows, but I'm starting to get a little fatigued with all the original series aliens and characters popping up. I thought it might have been stretching things a bit to feature the Gorn. It always seemed to me that Kirk was unaware of the Gorn in "Arena." It just seemed to me that the crew didn't know anything about the Gorn and their capabilities (which seems unlikely since Spock was on the ship at the time of their initial encounters with the Gorn). Though that can be fudged a bit more than featuring a Horta.