It seems very strange for me as a Japanese

At the very first time in main story, Frances Boyle is sitting on the ground in "seiza" style, next to Malcolm's body. I wonder how many American women can sit like this.

And,

In the bonus chapter, the back room of motel's front is "washitsu" - a Japanese style room with "tatami" and "fusuma". Why has typical American motel such a room?