All you've proved with that sentence is that you don't understand what Occam's Razor is or how to use it. It can not be used like you just tried to use it. It only works when both theories explain the same data. These do not since they both rest on fundamental assumption neither of which have supporting data.
So I suggest you go and re-read what Occam's Razor is before you attempt to use it on me.
DATA:
Shivan use a massive subspace field on Capella sun.
Sun goes supernova
Shivans loose a lot of ships in the process, including at least several Saths who were doing something to the sun.
Thrown conclusions:
1a. Shivans did something wrong, sun went nova before they planned
1b. Shivans did everything as planned (why so many lost ships then when there was no need?)
2a. Shivans opened a new supernode that somehow remained undetected that flung them somewhere far away (how would they select the destination? If a new node formes it will connect to some other system/sun in some strange relations with distance and gravity. Furthemore, why risk loosing so many other ships needlesly?)
2b. Shivans were powering a weapon that detonated prematurely
I rest my case.
And I notice that you didn't address my main point. How do you know how long it takes to detect a node. It could take months of work. The fact that at the start of the war the systems beyond Laramis were unexplored suggests that too.
It doesn't suggest anything. And a supernode should be far easier to find than a normal one.