From that document:

   This code implicitly assumes that vectors are indexed
   from 1; if dest starts at a different index than src,
   there is a chance that this code would trigger a
   segfault. (If you do get segfaults, to help locate the
   cause try running julia with the option --check-bounds=yes.)

So it comes with a tradeoff, namely that if someone else chose different bounds on an array other than [1..n] and you try to access it the standard way, you'll get a segfault.

This would scare me away from using anything other than the default indexing on an array in Julia.

Ouch, I didn't understand one bit of that document!