x11-toolkits/py-gnome-extras: PKGNAMESUFFIX usage

[barbara]

For curiosity, can someone comment/explain me about the usage of PKGNAMESUFFIX in x11-toolkits/py-gnome-extras?
My curiosity is originated by a problem I noticed with a "non-gnome" port. Refer to the following two messages I've posted in the freebsd-ports mailing list:
http://lists.freebsd.org/pipermail/freebsd-ports/2009-September/057098.html
http://lists.freebsd.org/pipermail/freebsd-ports/2009-September/057103.html

Thanks
Barbara