Unexpected behaviour of the modulo operator

I've noticed that the % methods on builtins behaves quite unfortunate (imo) when applied to negative numbers

Now, i am aware that mathematically it is undefined how it should behave with negative numbers, however basically every language i have worked in agreed that -1 % 10 should evaluate to 9.
This has the benefit that, when e.G. calculating a random ISize in a range 0 to 100, one would get away with rand.isize() % 100 rather than the more awkward rand.usize().isize() % 100 or (rand.usize() % 10).isize()

Similarly, when moving on a taurus positions could be calculated simply by something like primitive Up fun apply(x, y): (ISize, ISize) => (x, (y - 1) % 10)
compared to the more verbose

primitive Up
  fun apply(x, y): (ISize, ISize) =>
    if y <= 0 then
      (x, 10)
    else
      (x, y - 1)
    end

So I'm wondering if pony has any good reason for deviating from this behavior and choosing to return the negative remainder instead?