The Marantz 7C's phono section is based on the 12AX7, while the Shindo's is based on the 12AT7. Although the two tubes share the same pin-outs, their application data differs somewhat, making them cousins, rather than twins.
While the schematics probably differ (I haven't seen the Shindo's), there's a philosophical relationship in that the Shindo is using a classic tube (along with vintage caps and other parts) to create a (presumably) classic type of sound.
Plenty of other phonos use the 12AT7, including conrad-johnson, VTL, and Atma-Sphere. The 12AX7 is pretty ubiquitous, too. There are just so many ways to implement either one in a phono circuit, so you could say there's an abstract relationship between them, even though the construction and sound may not be the same.
Short of having the schematic on hand, who's to say that the Shindo was literally designed from the ground up, rather than being a reinterpretation of a classic concept.