I don't believe a dedicated forum for 'big-board' administrators is the way to go, least not here on XenForo.com.
That would surely feel to a lot of people that there is some sort of separation or l33t status 'big-board' administrators have. Maybe it would even make some people think that 'big-board' administrators have pushing power over the software.
This community, the software is all about the entire community, nobody is different.
I think there is some complement for that point of view.
A big board forum is needed so people that have forums with 500,000+ posts can talk between them, share experiences and share common issues, without interference from the users that are not having the same problems and that cannot really contribute to the conversation.
If someone with a big forum posts a problem, people might not see the point and reply with an uninformed opinion, because they have not run personally into the problem, or don't care at all, which makes sense. There is nothing worse than having a deep concern one has dismissed by a group of people that are just not interested, because they are not in the same stage.
It is not the same to manage a community with 10 moderators as one with 200. It is not the same to search in 20,000 posts than to search in 1M. It is not the same to have 40 forums as having 2000 and having problems with permissions and cache.
Regular users might not need memcache, a dedicated image server, a specific compiled version of PHP, might not care about using apache, nginx or lighttpd. Regular users do not want to weave the hooks into a precompiled php binary file. Regular users do not care about compression in the memcached stored content.
By not having a dedicated forum to big board owners you are exposing normal users to threads and concerns that do not apply to them
By not having a dedicated forum to big board owners you reduce the motivation for them to share their problems and solutions because they do not want to waste their time arguing with hundreds of users that do not have the knowledge or interest
I don't think they should put everyone in the same bucket. It is not healthy nor fair to anyone.