I looked at the source code for Pod::Perldoc yesterday and was also surprised to see =head being treated special explicitly in the code. In particular, subroutine containspod opens a file and looks for m/^=head/. It feels to me like that ought to allow for any of the POD commands, but certainly =pod. Perhaps that would violate some aspect of the spec, though I haven't been able to find anything suggesting that POD has to contain a =head1 command.
I don't know if this qualifies as a bug, or if it's intended behavior. It is a little surprising though.