I absolutely agree with you that consistency is an issue, but I have a hard time seeing how the PDGA can actively enforce this. The PDGA does not have the resources to set up shop as QA/QC within disc manufacturers.
I do like the idea of random spot checking. The PDGA can go to a retailer, randomly grab a stack of new discs and put them through the standard testing (flex, weight, etc.). Again though, this requires resources. I've worked in a laboratory environment for 10+ years. If a sanctioning body is going to levee some kind of sanctions against an equipment manufacturer, it will have to set up Standard Operating Procedures (SOPs), internal QA/QC and be subject to audits.
I believe the importance of technical specifications must be put in the hands of tournament directors, but I also understand the headache this would create for tournament directors.
I don't believe there is a correct answer to your question. I believe it is something that must be addressed, but it is going to take valuable resources to come up with any kind of viable solution.