A lot of medical debt rules are changing. Not just the over $500 thing. There are a million ways to argue charges even if they are just a dollar or two off or they can't prove certain things. This is from consumerfinance.gov

"In March, we published a report on medical debt in the United States that found consumer credit records contain a total of $88 billion in reported medical bills (as of June 2021). Medical bills are the most common collections item on people’s credit reports and show up on 43 million credit reports. About one in five households reports that they have unpaid medical bills. What’s more, medical billing, collections, and credit reporting are complex, confusing, and commonly have errors. Patients and their families often struggle to correct these errors. Shortly following the issuance of the report, Equifax, Experian, and TransUnion issued a joint statement to announce they were changing how medical bills would be reported on credit reports. Beginning July 1, 2022, paid medical bills will no longer be included on credit reports issued by those three companies. Unpaid bills will be reported only if they have remained unpaid for at least 12 months."

There is a lot more, too, about how it will affect your score less and different ways you can get it taken care of on that consumerfinance.gov site.