Primarily, how did the 92 come to be thought to have a genuine 30 Minute run dry capability
Answer - due to manufacturer's sales / publicity material such as was posted last month on this thread, such as was put out at various presentations on the machine, and a Program Manager who would do nothing to dispell the myth.
The answer to your last but one point is harder, we will only know if/when transcripts of the radio conversations and CVR are analysed in TC's report.
But we are lining up a fair list of parties to blame: Sikorsky, the FAA, the JAA, EASA, TC, Cougar Ops, Cougar pilots, the oil companies (those with aviation departments who were aware of the Oz incident). As usual with an accident, it could have been stopped if any in the chain above had acted properly.
The 225 has 30 minute running time after all loss of gearbox oil, using the emegency glycol system. I suppose that is not dry running, but if you want to be pedantic about it there is no requirement for dry running, just running after loss of all the oil. If that system doesn't work, you get a red light to tell you to Land Immediately - its brought on if either the glycol pressure or the air pressure used to atomise the glycol, falls.
HC