> I figured it's how they were able to weaken a chess engine back in the day; can't adjust the overall strength, so add random blunders.

In tom7’s Elo World, he does this (“dilutes” strong Chess AIs with a certain percentage of random moves) to smooth the gradient since otherwise it would be impossible to evaluate his terrible chess bots against something like Stockfish since they’d just lose every time. https://youtu.be/DpXy041BIlA?si=z7g1a_TX_QoPYN9b