Hi, I bought a CPO 2015 with 32,000 miles. I asked the dealer if they change all the fluids. They said no, unless they feel it is necessary. I scheduled a transmission fluid change and asked if they change all 12 quarts at that time. They said no, that is not until 60,000 miles -- this is just a 4 quart drain and fill.
Since I do my own maintenance, I changed the transmission, transfer case, rear differential and brake fluids. Again the dealer said "unless they feel it is necessary". All the fluids were brown like used motor oil which is different than the new fluids. When I say brown, that is no exaggeration.
With all that said and from my experience, 30,000 miles is a change all the fluids point - either DIY or dealer.