From an engineering point of view, the gas from Scarborough is...

From an engineering point of view, the gas from Scarborough is not suitable for KGP. KGP is designed to process a richer hydrocarbon stream while Pluto gas is very light. For example, KGP has several different product streams including ethane, propane, butane and condensate (C5+) separated via fractionation units. These are all heavier than methane. On the other hand, Pluto is very lean with a high Nitrogen content, which is lighter than methane.
The very low CO2 content of Scarborough (0.1 mol%) would also be a factor and would impact the performance of the AGRU (Acid Gas Removal Unit), designed to handle a higher concentration of carbon dioxide.

Ultimately, the KGP processing units have been designed to handle a heavy composition and the equipment is not sufficient in handling the lighter gas. I do know this option was looked at by Woodside but the plant modifications got too complex. Hence it was easier to build a new train at Pluto specifically designed to handle the Scarborough composition.

Browse on the other hand has a relatively similar composition to NWS gas and thus the plant modifications are a bit more reasonable. Thus, the preferred option.

In saying that, I don't disagree with your theory and I am sure there is lots of politics going on behind closed doors to get this project over the line. There will be pushback from every direction, especially in the media.

The other thing to watch out for is the relationships between the JV partners at the NWS. It is well known that getting anything done at KGP is quite difficult because you need 100% buy in from all partners. I have heard Chevron in particular is quite the pain.
For those partners who don't own part of Browse (Chevron, Shell, Mimi), maybe they don't want to spend billions of dollars on plant mods to process someone else gas (Woodside, BP) which could also hold up proceedings? This is pure spec of course.

I personally hope Browse goes through. Having Woodside and BP on our side pushing the gov to lift the onshore export ban can only be good. Browse wouldn't start-up till early-mid 30's so we would have 5-10 years of LNG export