He said he can neither confirm nor deny it at 15:42. It’s entirely possible that it was the brainchild of Sega of America. I think the 32x may have been the brainchild of Sega of America, but I may be misremembering.
32x was Japan ordering SoA to counter the Jaguar with some expansion, originally something like the SVP chip with extra polygonal power, but then SoA said they could boost the sound and video too if they are already doing that, and they sketched up the 32x on a napkin in a hotel room where they were saying. IIRC they may not have known that the Saturn was coming at the time, but then I wonder how the choice was made for using the same SH2s.
Note that the guy said nothing of this entire history. Does he even bring up the Nomad by name, or just that they were doing a portable megadrive?
For the Pluto, we know nothing of its origins, but the machine is clearly Japanese made, it uses sega of japans board numbering, even had a Japanese label on the inside. The boot rom and region are set to USA but that's a trivial detail (you can swap it in like ten minutes), and it could be that they sent one prototype to the USA while they had others in japan.
Mega Jet (predecessor to the Nomad) and Mega CD were also strangely absent. I always thought the Mega CD was the moon, but that was just a rumour because the cd player had a picture of the moon; the Japanese version just had some clouds.
I suppose neither of those had planet codenames. But then they did miss out two other planet codenames, Titan and Janus (moons of Saturn).