Arrays are sorted when using intarray subtraction operator

I've noticed that when using the `-` operator provided by the intarray extension, it appears to sort the results.
AlthoughI want the results sorted, I'd expect to have to additionally use the `sort` function it provides, as this
behaviorisn't documented.  I don't want to rely on undocumented behavior, although it would simplify my queries to do
so. Is the documentation lacking in this detail, or is it an unintended bug? 

Thanks,
--
Casey