Bots not playing at their rating


Rating bots is difficult because it is difficult for the programmers to force them to play bad moves in human-like ways. They can play for many moves at a relatively strong level and then suddenly throw out a completely awful move.
Computer bot ratings aren't set through playing millions of rated games against real players. They used to be set that way but some people took advantage of their known faults to farm ratings.

Not any more. They stopped that several years ago.