Paid charges for dental crown in full. Received bill weeks later for $519 "Insurance Reconciliation"

I had a dental crown installed in January. After the appointment, I paid the full balance for the crown $973 and was told I do not owe anything.

I received another billing statement today with an “insurance reconciliation” line item charge of $519. My explanation of benefits shows that $1,492 is the “billed” (perhaps contractual) amount for the crown, but my insurance plan does not cover crowns at all. The dentist just submitted it anyway.

When calling the dental office, they agreed to waive the $519 immediately as a “one time offer” but claimed that they are legally required (due to some law change within the last 2 years) to reconcile for whatever the insurance says. I can’t find anything online to corroborate this though.

It doesn’t make sense to me why the charged amount would ever be lower than what is billed. On my statement from the dentist, $973 was clearly the charged amount.

Can insurance companies actually require dentists to charge higher than they originally were going to (even for a procedure that isn’t covered)? Or was my dentist misrepresenting the $973 charge and then billing $1492 in the background? The billed amount of $1492 on the EOB does not align at all with my statement from the dentist. I would have expected to see their full amount on the statement. I appreciate any help in understanding this situation.

Original statement on day of procedure: https://imgur.com/vYvizjM

Billing Statement with Reconciliation Charge: https://imgur.com/Db9qsLQ

EOB from dental checkup: https://imgur.com/AeJ8RPR

EOB crown: https://imgur.com/fBJBW3E