Does this have any connection with my question or is this just an observation of my code comments?
In any topic that contains the words why, doesn't, my, code, and work, in that order, with few intervening words, the whole of the code is fair game for analysis.
Often, the comments are an indication of the way the poster thinks the code works. When they are wrong, it is only right to point out the discrepancy between what the comment says and what the code does.
Your offer a statement that the interrupt is detached for a long time.
And, I showed all the code that happens during the do-not-interrupt-me period.
Is this why a see a limit at around 7000 RPM?
I think so. For a large percentage of the time, you are ignoring interrupts.