How can there be an arc between braking and turn-in? An arc can only happen if you turn the wheel. You’re saying that turning the wheel to induce an arc isn’t turn-in? And how can there be acceleration before “final acceleration”?
From what I can tell, you are saying that because of traction limits, drivers over-slow the kart slightly as the grip transitions from braking to turning because you have to as you are using your front tires slightly to slow the kart, therefore you cannot be on the limit of turning grip. Am I understanding?
In driving you need to make as few inputs as possible. You brake, turn-in, once the kart is “set”, you straighten the wheel and roll into throttle off the corner. The lift of the inside wheel will float the kart off the corner and you can keep the steering wheel straight.
If you brake in a straight line, you are never using the fronts to slow the kart and all grip from the front tires can be used to turn the kart, offering maximum turning performance. But you can lose out on entry to someone who is trailbraking and braking later into the corner.
I think you have a tendency to vastly overcomplicate this. It’s all a balance and there are many different ways to attack a single corner, let alone the hundreds of different corners out there. Some drivers drive harder on entry and give up some on exit, some drivers brake earlier and get on the power earlier and gain on exit.