Oh, so M is not a stock-market-optimizer it's a verify-that-stock-market-gets-optimized-er.

I'm not sure how this differs from a person just asking the AI if it will optimize the stock market. The same issues with deception apply: the AI realizes that M will shut it off, so it tells M the stock market will totally get super optimized. If you can force it to tell M the truth, then you could just do the same thing to force it to tell you the truth directly. M is perhaps making things more convenient, but I don't think it's solving any of the hard problems.