Why would someone with millions not at least have an ACA plan? Even the worst ACA plan has an out-of-pocket max of around $10K individual and $20K family.

Personally, I don't trust "words from an insurance company." My health insurance company has more money and lawyers than I do. If I get cancer or something and they want to drain my life savings, they probably have some words on page 561 of my insurance policy allowing them to do it. What am I going to do about it, hire an attorney with my $0 balance and sue them?

Can you pay some "insurance of insurance", where someone guarantees they will win your fight, otherwise they lose a big chunk of their money as collateral?

Out of pocket maximums and limits (or aggregate limits) are two different concepts. Once the insurance plan's limit has been reached, it doesn't matter how much you've paid out of pocket.

The ACA does prohibit these limits for certain "essential health benefits", but there's a lot of wiggle room that insurance providers will take advantage of.

ACA plans don’t have lifetime or yearly maximum payouts. As long as the services are covered services, they’re obligated to pay beyond your out of pocket maximum.

With millions you buy health insurance.

Along with several other supporting insurance plans that backstop your health insurance and potential healthcare costs in extreme scenarios, and so on.

I mean, are you referring to long term disability? You can, it depends on what standard of living you want in the case both your legs fall off.

In actual health insurance, there is no longer a coverage cap. So you don't need a backup insurance plan past 5M or somethign anymore.