I agree! According to the Canard Pusher #65 page the mechanism was designed by Herb Abrams (an Ohio Solitaire builder, he passed away in 2013, may he rest in peace). Kjeld Pedersen and Ole Ploug (the builders of the Solitare in the videos) might have contributed to it (the CP article is not entirely clear about this). The mechanism allowed the use of a larger prop compared to the simpler fold-out mechanism designed by Rutan which increased the efficiency of the motorised flight mode.
If anybody has any technical information on the mechanism (plans, descriptions, photos...), please post it here or send me a PM.
Apparently Mr Abrams was a glider instructor; if anybody happens to know a former student or anybody who knew him, or even his family, it would be great it you could ask whether anything about the whereabouts of the plans is known. Clutching at straws here, but you never know, sometimes the world is a surprisingly small place...