The credits at the top of the cover say "Johnson/Balboni," so presumably the writer is the same but the interior artist is different.
And I think some people are expecting too much from the cover art. It's not meant to be a formal technical diagram, it's just meant to be a piece of artwork conveying the impression of being a technical diagram, as part of an illustration for a story centered on Scotty.
Oh please, no one on this
board would get in a snit over something like mismatched diagrams on a comic.
I did like issue #15 though, the entire series has been good as far as I'm concerned. I didn't go in with high expectations so i've been pleased. Liked the 'Cupcake' story & the look we got into Keenser's past.