No, the JTO Makuta model definitely came from Lego set designers, albeit not necessarily the same team that made the G2 sets.
One of the set designers is here on the Boards, and commented on the reverse-engineering topic for the model years ago:
Some of the designers involved in the various Makuta builds are credited in this reupload of the Makuta Contest video:
Also, the designers of the JTO model, specifically, are credited in these instructions:
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