You're right of course. Not intentional.
0:3 picks out index 0, 1, 2.
So 1:3 picks out the second and third element, which are indexed by 1 and 2 respectively.
My guess is that what one prefers probably depends entirely on the data structures one works with most....
I don't think that's right? It should pick out four things, not three.
Of course, you could argue that getting that wrong proves your point! I personally still prefer 0-indexing, but I definitely agree with you that having an exclusive upper bound is confusing.