Oversight doesn't matter - they're investing in the same investable universe you are, plus a handful of other minor classes that are highly correlated to all the things you already invest in. If a catastrophe hits that's sufficient to wipe out a well-diversified portfolio of publicly traded companies, government debt obligations, and real estate, the fact that the insurer also owns a few buckets of mortgages and writes life insurance on the side isn't going to sustain it and allow it to continue to pay your annuity. It offers no meaningful protection against black swan events.