Because this is how it works:

When you click on 'register' for sage you got teleported to a neutral server together with whoever else clicked on 'register' (that's the reason why you can't chat in group anymore, because there's no group in the neutral server, and why you can talk in world chat with people that won't be in your battlefield).
At that point starts an SWB with all the people there exactly like it would start in a server with more than 75 people that registered there.
Lets say there are 300 people registered. This mean the number of sage world battlefield that start at the same time will be 4.
How are people divided there?
1-3 go in 1st field, 4-6 go in 2nd field, 7-9 go in 1st field, 10-12 go in 2nd field, 13-15 go in 1st field, 16-18 go in 2nd field and so on until top 150 fills the two battlefields. 151-300th get split in the same way in field 3 and 4, with the difference that for 'top' placement they mean first level 90s are selected, then after the weakest level 90 is placed that way the strongest 89 follows and so on until weakest level 30 that registered.


About the thread starter, none here understood why they couldn't add the option that if an SWB could start by itself then that server didn't go in the cross server circuit. They did things in a * way like always.

Sadly there's no way to prove what i'm saying right now with our current accounts, but is a conjecture that makes sense with all we see out there. Could be is not exactly that way, but could be is very close to that one. I know i lack evidence, but is not true that conjectures don't help. Conjectures let other people that didn't think about it gathering the evindence i miss there or let other people figure out how the things are in truth if they aren't exactly like i said but close to it.
Anyways, if we want to prove this 15 or 20 of us could create 200 alts in the newest server in our region (that should be out of the cross server circuit) and see what happens when we join in the SWB to know exactly how we are distributed there.