The sample size is still small so everything can change with a mini hot streak, but...
Tatum's, MP, USG%, FGA have all steadily increased over his career. To this point he has been able to maintain his efficiency. Maybe he has "topped out" or plateaued in this respect. At some point more volume doesn't equate to more production. He's taking 2 more shots a game. If they are mostly misses his stats are in line with his career stats.
The Olympics, more pt, increased pressure, it's understandable. Maybe he needs to back off ever so slightly or battle thru it to get to the next level.
The glass half-full side is he has improved rebounding each year and the trend continues this year.