Ah, I see. The increment is so they can manually handle the included feature of the other cases, which number of the iteration you're on. Nice that it will automatically loop across a collection, annoying that they couldn't go the whole way and you need to deal with it manually.
Their C++17 example prints starting from 0. Probably a mistake.
If you look at the linked page for C++20[0], other types can be put in the initializer statement, so it's unlikely the loop auto-increments.
[0]: https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/p06...