As an interface wiring guy, I see both sides of the tinning issue. I have generally preferred to tin wire going into terminals, since it ensures that you have all the strands together, and it eases insertion. But, it does create a likely point of failure, in that you've created a more brittle section of previously very flexible wire. Manufacturers of such terminals, like Phoenix Contact, usually specify that you *do not* tin. The additional surface area argument is a good one, too. My follow-up suggestion is to make sure to provide strain relief on wires connected to terminal blocks on your sleds where possible - small cable clamps, or even small nylon cable ties around the wire and through holes in the sled. If the wire can't move near where it's inserted into a terminal, it's far less likely to break. Good wire management just makes everything more reliable, easier to troubleshoot, and looks nicer.
And John, thanks for another great contribution with this video!
Mark