You guys are missing the point. The designs
are all based on Ainu culture. And that also goes in the Starter choice.
As noted by Japanese fans on Twitter, the Starters seem to have been chosen because each one represents something important to Ainu myths.
Rowlett: Owl.
Cikap-kamuy.
Cyndaquil: Volcano.
Oshawott: Otter. Otters are messengers between humans and the gods. An otter also
had a role in the creation of humans.
Kaihatsu, who has knowledge of Ainu
goes into more details and includes references to other Japanese non-Ainu stuff, but Japanese fans seem to be focusing exclusively on the Ainu angle.
It's not feudal though.
It's late Taishō to early Showa. The Taishō era ended on December 25, 1926, with Emperor Taishō's death. And according to franchise lore, Professor Nishinimori (Westwood) invented Poké Balls in 1925, so it fits the time frame. Nishinomori is also regarded as the "father of Pokémonology" in Japan (yes, Japan. Details about Nishinomori are given in a book from Gen 1, when
Pokémon was still an alternate history Earth instead of the fantasy world it was retconned into).
The Professor might be Nishinomori, or maybe Nishinomori II, since Nishinomori I was retiring due to age when he discovered Pokémon could shrink. The anime says Nishinomori's lineage goes until
Nishinomori V, at least.