My wife and I did this event in our LJ in 2020... it was a blast. The guides were amazing and they had a ton of them. I counted over 20 breakdowns the first day but they got everyone to camp.
Some things I noted...
As to needing an aftermarket diff cover, that was JK specific as it seems those have a lip on the OEM one that catches, and they were dealing with too many needing fixed on the trail.
As to not allowing older Jeeps, this goes again to them having to deal with too many break downs, and harder to get parts. They offer to fly in parts for breaks on this trip via helicopter at no additional cost to you (you just pay for the parts) and they'll help with the mechanical repair or do it for you. It was getting to hard for them to do with with the older Jeeps.
As to the comment they were trying to somehow limit attendance by requiring larger tires... nope. The event sells out in less than 15 minutes even with their requirements... the requirements are all about trying to get 100 Jeeps through the trail in a day in less than 12 hours.
They have like a 40-50% newbie rate on these runs... their goal is to give people a good time and get them through the trail without incident wherever possible, and they do a good job of it.
Even when it was 35" tire requirement when we went, of the 100 Jeeps there were only 11 TJ/LJ's.. most were JK's with some JL/JT mixed in. Our LJ on 35's looked small in that crowd.
All that being said I understand why they do it from a business perspective, but you don't need all that to do the trail, I never had issue, never got stuck on my 35's
Going back there this summer (along with other trails on a 10 day trip) with a small group of club members and looking forward to it!