That doesn't really answer the question asked, though, Mirikon.
The question was "why is an elf, oni, or cyclops classified as a homo sapien, but a sasquatch isn't?"
To truly answer that question, we would have to talk to the minds behind some of the original creature/racial rules for Shadowrun and the get the reasoning behind them. But if I had to take a guess, I would say it is based on the source material, mythology.
Sasquatches, or Bigfoot as they are often called in American folklore supposedly pop up from time to time even recently. They aren't magical creatures of a distant past. So, the concept that they exist separately from humanity made sense. Same thing goes for Pixies, which is another example of a metasapient in the Shadowrun lore that sort of just appeared out of the woods one day. All the other (playable race) metasapients are basically just awakened animals. Centaurs are more closely related to horses than people, and the same goes for Naga. And of course Shifters are animals first, that can shift into humans.
Another possibility is based on how closely some of those species resemble or relate to animals instead of humans. Oni, Cyclopses, Satyrs, dwarfs, etc all resemble humans in many depictions. In modern fantasy games, a lot of them are considered "playable races" placing them on-par with humans. The only SR playable metasapient that even closely resembles humans is the Sasquatch, which we already covered as having a good excuse for being kept separate from humanity as a classification.