port dependents

[David Evans]

I'm having trouble understanding the behavior of port dependents.  I'm
sure it's a well known situation
so perhaps someone with more knowledge can explain.

Here's what happens:

port gcalctool 2.26.2 is initially installed and it really does depend
on  libgnomeui.
port dependents libgnomeui says that gcalctool is a dependent of libgnomeui

now I upgrade to gcalctool 2.26.3 which no longer depends on libgnomeui

sudo port upgrade  gcalctool

this deactivates gcalctool gcalctool 2.26.2 and installs gcalctool 2.26.3
port dependents libgnomeui still says that gcalctool is a dependent of
libgnomeui

OK, I think, maybe it's referring to the 2.26.2 version which is still
installed but inactive
so I uninstall that one

sudo port uninstall gcalctool @2.26.2_0
but port dependents libgnomeui still says that gcalctool is a dependent
of libgnomeui

Is this a bug or a feature?
What is port dependents telling me, if anything?
When dependencies change, how does port dependents get updated?  Or does it?

TIA for any help

Dave