Sasha did both SA & SC - at least in 2002 and 2003 plus CoR (2002) and Trophee Lalique (2003) (as TEB then called) as they used to do 3 GP back then to qualify for GPF but it was an exhausting schedule
Yes, it was, and if I was Papadakis & Cizeron, I would find it quite exhausting to train in Canada, fly to France, fly back to Canada, fly to Japan, and fly back to Canada. (Before, yes, flying back and forth for the GPF, their own nationals, Europeans, and then Worlds. It's a really tough schedule. Lots of athletes do it, but usually when you are the World champion, you can at least choose to do one event on the same continent where you train. So for them, I can actually see SC (close to their training home and technically an option unlike last season) or Rostelecom (which they could do right after TEB without having to fly back to North America) as a possibility. An unlikely possibility for all of the obvious reasons, but I'm not sure doing two events in a row would be more exhausting than the back and forth.
In the Mikhail Kolyada fan fest thread it's been reported that he will do Rostelecom and either Cup of China or NHK, pending Hanyu's decision, and that he turned down Skate America. Since Hanyu is a 1-3 seed and Kolyada is a 4-6 seed, not sure why Hanyu's decision would factor into Kolyada's second choice of Grand Prix? Also, since Adam is also a 4-6 seed, it seems odd that Kolyada was even offered SA.
And this is why logic doesn't always work! Maybe Rafael, Ashley, and Adam just prefer SC. (If I was Adam, I wouldn't).

Though I would send W/P elsewhere.