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.

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?