The dates would seem a little bit off. In an fairly recent interview with Walter Seer, owner of Seer Sound and in the 60's a sales rep/agent for Bob Moog, he told the story of how the band (sans Brian) came to see him about buying a Theremin to take on the road. He offered one, but no one could play it. So he contacted Bob Moog (his boss) with the issue, and Moog in response came up with the Ribbon Controller unit (taken from an available option on one of the early Moog modular synths) mounted on that stand which we see Mike Love playing in concert from Fall '66 onward.
It was stated specifically that they needed a solution for performing "Good Vibrations" live on stage. There was, at that time, no other reason nor use for taking a Theremin on tour, as Brian had only ever used it for Good Vibrations and "I Just Wasn't Made...", and the latter tune was not even considered for a live performance in '66. They first approached Dr. Paul Tanner who played most of the Beach Boys' Theremin parts on the recording sessions from 66-67, including Good Vibrations and IJWMFTT, and was the only one who had the Electro-Theremin which was his own one-of-a-kind design. But Tanner turned down their offer to tour - basically he'd be on stage for one song and that's it. And they couldn't take an Electro-Theremin (Tannerin) with them because Tanner had the only one.
So Moog's timing is a bit off...if you believe Walter Seer's account, and he was the guy who the band approached with their request.
The Ribbon Controller option can be seen listed in the Moog catalogs as an add-on module I believe dating back to '64, but connecting the Beach Boys to that in '64 seems not to agree with the history of Good Vibrations, Seer, etc. With all due respect to Bob Moog, of course...
It could just be a mistake on his part.
Any thoughts on this?