The theory that "less abusive" conditions make a difference is probably wrong, and I can tell you why.
The thing that matters when a strap or other connector breaks is the applied force. When it comes to things like ropes, engineers and physicists use the word "tension" to describe force. It's the same thing. A strap will always break at the same level of tension, no matter how fast the tractor is going. If a strap's breaking strength is 1000 pounds, it should always break at the instant it reaches that level of tension, regardless of how the tension is applied.
Energy is stored in straps and other objects under tension through stretching. The amount of stretching--the displacement from the resting position--is going to be exactly the same at any given level of tension, so the amount of stored energy should be exactly the same. When a strap breaks, stored energy is turned into kinetic energy--the energy of motion--and a given amount of stored energy will always produce a fixed amount of kinetic energy, which means a fixed maximum velocity.
If you break a strap at 2 mph or 20 mph, you should end up with the same broken-strap velocity, except for whatever tiny contribution might come from the extra 18 mph.
If you break a rubber band slowly or quickly, it will still send its ends flying at very high speed.
A tractor moving at high speed has the potential to apply more tension to a strap because force is the time derivative of momentum, which is mass times velocity. When a fast tractor reaches the end of a strap, it has a more momentum than a slow tractor, and the momentum is applied to the strap faster, so you would expect more force. This is why jerky movements break things. The strap can only handle so much force, though, so the force applied to the strap will limit out at the strap's breaking strength regardless of the tractor's speed.
I am right about the theory, but because my training is in physics, not engineering, I may be wrong about the breaking characteristics of straps. Unlike engineers, physicists don't learn much about real objects people actually use. For all I know, there are real-world characteristics of straps which would cause them to behave strangely when forces are applied quickly.
The big lesson I'm taking away from all this is that the only real answer to the problem is to use an oversized strap or chain your tractor can't break. If there is a better answer, I haven't seen it yet, and it looks like the Youtube people haven't either.
I don't think my 37-HP tractor could break my strap at top speed, and I don't jerk it anyway. Hope I'm right. I bought a very thick strap in order to avoid problems.
