It feels like you are intentionally missing the point. The blog makes it quite clear that the purpose of notifying AWS is so they stop charging you for that specific type of traffic. How else would they know whether the spike is normal production usage, which is billable, or part of a migration effort?

There is nothing in the blog suggesting that this requires approval from some committee or that it is anything more than a simple administrative step. And if AWS were to act differently, you have grounds to point to the official blog post and request that they honor the stated commitment.