To clarify, the sample sent to Austro gets analyzed, and if there is an issue, they get back to you with recommendations. If not, you hear nothing. I'm at the Diamond Canada facility right now taking the DA42 Austro course, and made my displeasure with this lack of communication clear.
Please understand that if you choose to send a sample to an outside analyst for feedback, it is in addition to, not replacement of the requirement to send the sample to Austro. Not sure of the warranty implications, but would lean heavily toward sending the samples for at least the first 3 years. Personally, I will send them every time, since Austro knows their engines better than Blackstone does.