https://w.atwiki.jp/sakuga/pages/1377.html
北爪宏幸 - 作画@wiki
>1：エルガイムなどのHMの作画については、永野護氏の設定に合わせ関節のギミックを意識した動きをつけている。（グレートメカニックのご本人のインタビューより）

This shows that at least Hiroyuki Kitazume was not only in charge of character drawing but also mechanical drawing.
It's also possible that he modified the drawings as an animation director, but I'm guessing that he was in charge of Genga this scene, since this part looks similar to his drawings at the time.