Why exactly can't I transfer my characters to Grob?

The current plan is here:

However I too still have questions about the locked servers.
It isn’t clear to me that SoM characters will actually get to bypass the lock so I have questioned that in a different thread.

“So now my question is does this mean that realms that are locked now are planning to be unlocked by the time SoM transfers are enabled? Or will those locked realms still be unable to receive transfers? Because if you are allowing SoM characters to bypass locks this is extremely unfair to those on the locked servers that want to get all of their characters currently in Wrath consolidated on their main/locked server.”