This is exactly right. When you disagree with a supplier you can only disagree based on the contract, and if someone could reasonably (and there is a wide latitude here for "reasonably") argue their interpretation was within the constraints of the contract than your remediation options are limited.

If you read contracts a lot (and over the years I've probably read a couple of thousand and negotiated maybe 100 or so) you will begin to see clauses that are in the contract which specifically prevent what was clearly a problem before that had not been decided as being in breach, so the added clause insures that in future contracts it would be decided as being in breach.

My lawyer once told me that every contract tells a story if you know how to read it. The more I've read, the more I have come to appreciate that sentiment.