I will make this short

It seems like the independent body movement that Whis mentioned during training is the technique of the gods

He said that Goku and Vegeta need to master it if they want to get close to Whis. He also said Beerus has NOT mastered it yet

Now jumping to the ToP we know that there is a mortal stronger than Beerus, we also know that Jiren will be the main enemy in the Tournament

And we also know that Jiren moved out of the way of the arena parts with closed eyes, his body simply felt the danger and reacted

So it is reasonable to assume that Jiren is the mortal that is stronger than his GoD and Beerus because he has mastered that technique

Going back to the new Goku poster one description says: " The work of the gods ends here" it could also mean "the technique of the gods in final/perfected"

If we take the second meanind, then it seems like Goku will also break his mortal limit at master this independent movement (muscle memory) for his body and with that challenge Jiren, which noone else could