I don't want to be an a** but I'm having trouble understanding what you wrote. What does a loop have to do with him being solo or not?
And why would you want to cut the engine on top of the loop?
If you watch it, he is cutting the power at the very top of the loop to get the nose to "swing" (for a lack of a better word) down faster and then as soon as it does so, he is going to full power to finish the loop with.
I use this trick for my RC flying when doing loops close to the ground (just like he was). now not knowing much about ultra-lights, it also might be for other reasons such as not overspeeding it and ripping it apart (that is a complete guess, i dont even know how fast the dam things can go).