I said this in another topic, but it probably should have been here, instead. In "The Apple" the landing parting is specifically seeking the natives of Gamma Trianguli VI. An earlier survey had already been conducted of the planet. Now, while we don't know what that survey revealed, I think it's safe to say that even the most basic of surveys would be able to determine that the culture was living at a pre-warp primitive technological level.
Yet Kirk was ORDERED to make contact with the natives in order to deduce what the unusual readings were that the previous survey detected. So, Kirk was ordered by Starfleet to make contact with a primitive culture, and Kirk did so without any attempt to blend in with the natives and did not hide their advanced technology.
Just like Errand of Mercy. No attempt to hide their origins, clothing or tech. The only difference is that in Errand of Mercy they beamed down in a town square, in The Apple they beamed down unobserved.