You haven't given any reason to explain why you think the existing docs are wrong, nor any reason why you think your version is better. Just stating that the docs give "misinformation" is not good enough.

By your matrix, 'Python'[0:-1] should take a slice starting from the left of 'P' and ending at the *right* of 'n', returning 'Python' unchanged. According to the original, documented matrix, 'Python'[0:-1] takes a slice starting at the left of 'P' and ending at the *left* of 'n', returning 'Pytho'. without the n, which is what actually does happen.

You should also consider the slice 'Python'[-6:-5] according to the documented matrix (returns 'P') and your matrix (returns 'y').