Puzzling inconsistency regarding dep

[MK-MacPorts at techno.ms]

Hi,

port gtk-doc puzzled me just now, since it doesn’t seem to have dependent ports.
—
$ port rdependents gtk-doc
gtk-doc has no dependents.
—

But if I let port show me all kmymoney4-devel deps it gets listed:
—
$ port rdeps kmymoney4-devel
...
  kde4-runtime
    kdelibs4
      soprano
        libiodbc
          gtk2
            gtk-doc
…
—

So, the question is, why the rdependants command didn’t spot this in the first place?

Greets,
Marko