Well then their protocols suck. I have many anecdotal data points about them fumbling in major ways when it matters (missed major pathologies, messed up surgeries, etc.).
If you have a choice of hospital networks, research carefully. Kaiser might be fine for many people's needs, it's not fine when it comes to intensive care.
The care quality of all major healthcare providers in the US is some pretty available data, and I've never heard anyone of being suspicious of Kaiser, of all companies. They're specifically known for having really good outcomes. It's like asking for a source that McDonald's sells the most burgers in America. It might not be true - maybe technically it's someone selling sliders or whatever, but it's so close it's probably not worth arguing over anyways.