Just an update that there's no update yet. I've contacted Hyundai via their web portal and have not heard back from them yet. I'm out of town for a few weeks, so I've left the car parked outside instead of in my garage. Not that I expect it to spontaneously combust. As I put earlier, I've driven several thousand miles in the car with the damage and have had no issues. I've also DC fast charged multiple times at the fastest charge rate in 100 degree+ weather. The car's battery cooling system seems totally normal, so I have no reason to suspect the cooling plate was penetrated.

My question after looking at those Munro videos is weather the air gap between the shield and the cooling plate is a sealed air gap, or is technically open to the elements?

 

Okay, I'll chime in. Also, just another random I5 owner with zero professional experience. No else has mentioned this, if the hole was in the middle of the battery pan cover, I would be more worried about something penetrating the battery case itself. Because the hole is on the edge where it bolts to a frame member (or something solid) it looks to me be be near impossible that the battery could be damaged. I do agree with the others that replacing the bolt and cover would be a good idea, if reasonable. Otherwise replace the bolt and fix the hole.
Your story reminds me of my own tail of woe. I had a beloved 1984 Accord, I had the clutch replaced in California and shortly afterwards we moved to Southern Oregon. After 6 months or so the clutch stopped working. I limped it to a well respected (I thought!) independent auto repair shop. They called me and said it need a whole new clutch assembly...
I got the car and took it to the local Honda dealership, they called and said the clutch cable was broken and quoted me a very reasonable price to fix it. I was their customer for many years after that experience.

 

You know, the thought did occur to me that the initial service place was trying to "take me for a ride", so to speak in telling me to replace the battery. But, I can't imagine anyone agreeing to $52,000 for a battery replacement when you can buy a brand new and more modern version of my Ioniq 5 for less than that. And, there's no insurance company in the world that would pay that when they could just write off the car and hand me a check for well under half of that amount for the current value of the car. Maybe they were just testing if I was monumentally stupid? It's like offering to mow somebody's lawn for $5,000. Probably not going to find many takers on that offer....

 

Another view of the battery chassis

 

Final update to this saga. I took the Ioniq 5 into a third service center to get it inspected. They agreed with the 2nd service center that the damage was superficial and nothing to worry about. They told me any battery issues would almost certainly be met with dashboard warnings and OBD codes (there have been none). So, I think I'm going with the majority here and considering the car fine. I've still been driving it throughout with no issues.