Thanks for that tidbit, I had to look it up. This wiki page (https://en.wikipedia.org/wiki/Bacillus_cereus) says, "Germination and growth generally occur between 10 °C and 50 °C, though some strains can grow at low temperatures". I just measured the rice in my Zojirushi cooker, and it read 70 °C.

Keep warm settings on rice cookers keep the rice above 60C to avoid bacterial or fungal growth.

I use the keep warm setting on a rice cooker for another reason: To make black garlic. Take 20 bulbs of good quality garlic, put it in the rice cooker, set it on "keep warm" (NOT cook!) for two weeks without opening the lid. Note the rice cooker will be useless for anything else after this because you'll never get rid of the ingrained garlic smell.