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I think it’s like a Bilenky Viewpoint where you’ve got the tandem setup with the captain in normal riding position and stoker in recumbent and I’m sure I’ve seen this on a bike where you can convert the front to kiddy friendly by adding the second (third) set of cranks on the front in a shortened position. That mounting point also lets you take the front cranks off completely and put a kiddy seat on instead, or a front rack like an Omnium.
And this nice setup in Saumur