Thank you for helping me understand the situation.
and it's also why Senators swear in immediately because they are not governed by the electoral act.
The situation for Senators is a free for all. I don't see in the North constitution when the North Senator swear in / begins its term. I don't know how they determine when the outgoing Senator leaves and new one comes in. (mutual agreement?)
Since every region coukd be like that and they don't always hold Senate elections at the same time, all Senators terms don't start at the same time (if there is even a specified moment for swearing in).