I understand what you're saying, and i'm not saying that you're wrong and that it wasn't a product failure, however it is important to prove that a product failed before slandering them online.
Unfortunately the Automotive industry is one where the blame is constantly being shifted (just ask any mechanic if they've ever made a mistake - they'll tell you that EVERY issue that they've ever had with a customers vehicle was due to a dodgy product), this is why manufacturers are reluctant with warranties as they will need to be sure that it was genuinely a product failure before handing out cash.
As I said earlier, I work in the automotive aftermarket and see warranty claims all the time where 90% of the time it is proved beyond a doubt that failure was due to fitter error, despite the mechanic believing that they know everything and did everything right.
An example of this is when fitting new radiators - A radiator may fail so they are tasked with replacing it, only for the new radiator to fail shortly after, which the mechanic will claim as product failure. It generally turns out that they didn't flush the heater circuit or there is stray current that they didn't even check for and was part of the cause of the customers original failure. Had they gone through the proper testing and flushing processes there would have been no issue, which is why it is fitter error.
The cost to prove that it was a product failure shouldn't be an issue, as that is what will allow you to recoup the far larger costs associated with the failed product. You might need to spend an additional $100 for testing, but once that's done you can recoup the cost of the clutch AND testing, as well as possibly the other costs that you incurred.
If you are positive that it is a product error rather than fitter error, then it should be a no-brainer to take it further and get a large portion of your money back rather than copping it on the chin. I'd even send the clutch assembly back to Exedy (which will cost f-all) for their assessment, rather than doing nothing.