I was pondering this very question while I've been watching The Long Way Up.
The DSR should've been at least mentioned and tested in the first episode (I suspect there may have been some T&C's from HD to prevent that maybe?)
The HD's had to be heavily modified to be trip-ready whereas the DSR's would've at least had a proper touring/offroad base to work from.
Like you have all mentioned money talks.
I hope in the future one of them opens up with the full decision making process.
I also have to say that Ewan and Charlie really disappointed me with their electric bike knowledge in the first two episodes.
They were joking about how they don't even know how to charge them and how surprised they were when the cold affected their range so much.
A week trip in Scotland (yes I know Ewan lives in LA now but he's not short of cash so he could have nipped across the pond) with a couple of electric bikes would haven given them much more info about how to ride/charge electric bikes before they headed off to South America.
Mind you, your trip is much less perilous when you've got a Mercedes Sprinter following you with a generator on-board
Having said that, I enjoyed the show
Anything that gets elec bikes into the limelight has got to be a positive..