"I have a 2018 Cummins and it tells me how many trailer miles I've towed."
Now that's a pretty cool feature.
As far as the bearings and the warranty, that will probably depend on the wording.
Some people, and after looking at the condition of my axles, I would be among them, that pulling hubs and checking the condition of the bearings, seals, and seal surface area on the axle should be done when you take possession of your trailer. That way you know exactly what condition your trailer's running gear is in.
I lucked out because when I pulled my hubs I saw how the parts had been thrown together in such a haphazard way it was amazing that more damage wasn't done to sealing surfaces and bearing areas. I think most people that have leaky seals have them because they were damaged when assembled. But that's JMO of course.