I would strongly suggest that anyone that doesn't know the exact age of the tires on their FGRV's check them today and plan accordingly.
Remember, it's age, much more than appearance & miles on the tire that is a leading cause of tire failures on RV's.
Here's how to find and read those date codes:
BTW: Passenger car tires, of the correct size and weight
rating, are not inherently going to blow out when used on a trailer, but they may not track as well as ST tires.
I'd guess that the tires on the trailer that Liz rented had other problems than just not being ST rated.