There's already a lot of technical answers here, but I'll answer a few of your questions anyway.
Yes it is impossible. You can to some degree see the difference in movement at the end of the Monitor Distance video, where it shows and 80% movement when the aims are matched at 25%.
The problem with acceleration is that it is not consistent.
If you are using a 1080p monitor and match 100% monitor distance from Windows to a game, it is calculated what sensitivity is needed to equal 960 counts to move to the edge of the monitor in a game. If you match 50%, it will match 480 counts to 50% of he monitor distance, and so on.
It basically means matching the smallest movement possible. You can see that the difference between 1% and 0% is virtually nothing, but there is a small difference.