It's intentional, if now regretted.

From Template-Toolkit/source/lib/Template/Stash.pm

#---------------------------------------------------------------------
+---
# undefined($ident, $args)
#
# Method called when a get() returns an undefined value.  Can be redef
+ined
# in a subclass to implement alternate handling.
#---------------------------------------------------------------------
+---
 
sub undefined {
    my ($self, $ident, $args) = @_;
 
    if ($self->{ _STRICT }) {
        # Sorry, but we can't provide a sensible source file and line 
+without
        # re-designing the whole architecture of TT (see TT3)
        die Template::Exception->new(
            $UNDEF_TYPE, 
            sprintf(
                $UNDEF_INFO, 
                $self->_reconstruct_ident($ident)
            )
        ) if $self->{ _STRICT };
    }
    else {
        # There was a time when I thought this was a good idea. But it
+'s not.
        return '';
    }
}
[download]