The recommendations in your owners manual were made by the people who designed and tested every component in your vehicle. They spent millions to come up with the various intervals.
BUT, they are only concerned with the first owner. They don’t make any money when you trade your vehicle in or sell it. New car buyers keep their cars an average of 11 years and about 150k miles, last time I heard these stats. It may have changed since then but I doubt it changed by much.
They also base their recommendations on average conditions. That being climate etc. They do have a different schedule for severe conditions and driving.
The dealer has not spent all this time and money to determine the best schedule, but in their defense, they do know the local conditions and if they are performing all your maintenance, they can spot conditions unique to your driving conditions and make some recommendations based on that. They may also recommend a change if you have either a history or have indicated that you will keep this vehicle longer than average, which you have done here.
If the variation in the schedule makes since to you, and I think that in your case it probably does, they you may want to follow their advice.
BTW, the transfer case and the front differential are very close to the transmission so they will get much hotter than the rear differential. Heat is the main enemy of oil. The rear differential may not really need to be changed as it remains much cooler, but should be checked at least.