TimToady stopped by the CB while this thread was being discussed, and said that by default the brackets always work in list context. He and some others pointed to S02:1377 as the documentation. I've not been keeping very current lately on Perl6, but I hope the link helps.
Comment on Re^2: [Perl 6] single-value vs. array slices
Yes, that very section in the documentation was updated already this month based on problems I found. The example was showing context changes in "other places", that is clearly against the rules now.