That's true, but I've never actually seen anyone call 'has' like that. Plus, Perl's behavior on lists makes sense (always flatten) if there's no mucking around with prototypes, so that's much less confusing than the behavior in the article.
The first one I presented is the way the Moose documentation calls has, the way the Moose test suite typically calls has, and the way I and most of the rest of the Moose Cabal call has.
The second one isn't common at all, but I have seen people both completely leave out the parentheses:
has foo => is => 'ro', isa => 'Str', ...;
or treat has as a straight function
has(foo, is => 'ro', isa => 'Str');
both of which cause Perl::Tidy to do weird things.
