Can't prove a negative… But the reality is, the NTSB and the various parties to the investigation have not yet reached a working determination of why the plug failed on the Alaska aircraft. Only yesterday was an inspection protocol even reached.

Your posts seem to indicate skepticism as to one of either a) representations made as to the design of the plug on the 739ER or b) whether the 739ER should also be grounded. I can tell you that the 739ER is absolutely part of the conversation, and may be subject to inspection, eventually, on some interval. But the practical and economic reality of the situation is that, to date, there have been no significant safety issues with the system on the 739ER, across a fleet of hundreds of airplanes, in totality, flying for more than 15 years. So there's no justification to impose what would be a more widespread, disruptive grounding of a type that's not directly implicated in the most recent incident. Again, that's not to say some inquiry might shift to the 739ER eventually, but it's not a pressing consideration at the moment.