Insurance EOB says I owe zero for a noncovered charge?

I had sinus surgery last month which consisted of a septoplasty and turbinate reduction. I haven’t received a bill yet from the hospital but I did receive an EOB with twenty charges listed as “SURGERY” with some large dollar amounts next to them. I only focus on the column for “what i owe” and the total listed is a few hundred bucks.

I didn’t even realize that one of the “surgery” charges wasn’t covered until today when I got a letter from insurance saying it was for “an implant used to release drugs” and was considered experimental. I didn’t even realize this had been done as part of the operation.

I go back to the EOB and the amount billed for this charge is $6,000+ which I absolutely can’t afford right now, so I am sweating buckets. But under the columns for “allowed amount” and “what i owe”, it says $0.

So what does this mean? Is the hospital likely to still charge me for this $6,000 procedure? Why send me this letter if the amount I owe is supposedly zero?