And as 2 years have passed, it's probably about time for me to wake up and stick my oar in, say why we've done things in the past, and just, generally, get people's backs up.
So here goes...
I'm not sure the justification should really be "FreeBSD have this category, therefore we need one stat" - the stunning proliferation of pkgsrc entries in the science category would seem to suggest otherwise.
Just to clarify what we've done in the past - we try to limit the number of categories that we have in pkgsrc. This is for sanity, cleanliness, brevity etc. We also try to have categories by subject area, not by other software it uses, although we fell flat on that one with the x11 category fairly early on. However, it's one reason we have deprecated the plan9 category, and the input-methods one too. And the specific language ones (sorry, specific-language folks, I know it's a pain), since that just doesn't scale. We used to wait for there to be a critical mass/escape velocity of packages which could be identified to go into a new category, and then repository move them all there once the critical mass/escape velocity had been achieved. That velocity was usually reckoned to be 10-12 pkgsrc entries.
We haven't tried splitting categories either, tempting though it is. Maybe that lies in the future.
Once the new all-singing, all-dancing version control software is available, the equivalent of repository moves should be back on the agenda again. I'd like to thank you in advance for any and all of the messages about version control software, and should say that those messages will be routed where the sun fails to shine, thanks very much.
Hopefully this gives more background as to what we were trying to do, and inform any future discussion about how categories have been managed historically.
(FWIW, I don't really like the categories distinction per se, but it came over when pkgsrc was started. It could better be done by keywords in the Makefiles, but that would leave one main directory with n-thousand entries, which is completely unworkable. Multi-level categories or sub-categories also quickly become unworkable. So a single layer of categories it is :) )
Best,
Alistair