He is relating to his fellow Earth humans by showing them a familiar setting which includes such things as oxygen (which he too needs) and light from the same sun he has known since his day of hatching. Perfectly normal.
Im a nobody and I always put up the fake background, even if its absolutely fake as hell. If I'm in the office theres potentially private information up on the whiteboards behind me. If I'm at home thats my private space and thats my business.
Greenscreening yourself is like one of the least weird thing about Zuck.