peac & love on planet earth
So this is interesting because entire thing is communication, and it also shows how important different threat/aggression postures are.
The first cat comes in ready for a fight. Low down, trying not to be seen, stalking/wary posture.
Second cat jumps in the air and then does the exaggerated arch. That's an absolutely terrified cat. No cool, no chill. A cat willing to fight would not have gone full arch because it's moving them out of a position where they could launch themselves at the other cat. However, a scared cat can move from this to a preemptive attack if they think the other cat is going to attack them and just moving slowly.
Realizing the second cat doesn't want a fight, the first cat comes out of the low, threatening slink quickly to roll around to say hey, whoops, they weren't here to attack, they don't want to fight either.
With similar speed and exaggeration as the arch, the second cat does the same wiggle that yes, I too have no desire to fight, look at me doing the same thing and conspicuously not attacking when you're vulnerable.
To function as a social species, you need checks and deescalation. Both cats don't have perfect information about the other cat, and they need to know that they could misread or be misread, and then adjust their behavior to fix the problem.
