I'm actually amazed that anyone would think that test suite files *ought* to be runnable from everywhere.
It certainly doesn't hold true for the test files of perl itself and I don't really see that it ought to hold true for perl, perl modules or any other package that contains a test suite.
But, I guess that those of us who are free to define our own expectations should simply be grateful for that opportunity and not get too carried away when the expectations of others don't quite match our own.