That doesn't mean anything. The rating estimate by the game review is just nonsense.
Professor Doctor Wumpus elo
I think you guys probably know this, but a couple things to note:
The bot's elo is 3100.
The bot can't handle scholars mate. (Proof below)
A number is written there doesn't mean anything. It's not a real rating, just a meaningless number. It can be anything, even complete nonsense like 1 (for Mittens).
If you beat him it shows the elo: 3100 (NO CAP)