Supposed liquid damage - no sign of it (photos)

I’ve seen this question numerous times so I went to take the logic board out of my macbook in order to follow one of the fixit guides and am now confused! Background to this is:

Macbook Pro 2015 13” died one day and wouldn’t turn on.

Took it to Apple who said logic board needs replacing (they didn’t mention water damage) and I would have to speak to the people I bought it from (KRCS)

Sent it to KRCS and asked for a warranty repair who told me it would cost £900 to fix as it was water damage. Fuming, it cost me £1200.

Looked online and saw that you can fix corrosion yourself in some cases. I’ve taken the back off the macbook and cannot see any water damage. I understand that it’s not always visible but hoping someone might be able to spot it for me.

https://photos.app.goo.gl/CPGneKVE5LowHW...

Hope the link works!