I've gone to other people's share shelf and seen things like Petaya berries and Apicot berries which according to bulbapedia hasn't been released to the dream world in any way. Meanwhile there are other 'event' berries that do have DW release data like jaboca berries and rowap berries so it's not like the data could be missing (could it?)
It is not possible to hack berries in the dream world because it is online and could result in being restarting or banned.
1]The could've hacked it but their are different release dates around the worldhttp://pokecheats.net/forum/showthread.php?13755-Pokemon-Hacking-Tutorials-The-Dream-World-Hack-(Automated-Pokemon-Items-Points)
If they did hack it, they probably used the link to do so.
But the release dates are different.