> I've recently met some garments by Endura using what they're calling "Expanded PTFE." (Polytetraflouroethylene methinks, aka Teflon.) I've looked at test graphs apparently produced by the US government/military which show this fabric to be significantly more breathable […] than eVent.
Gore-tex and Event are ePTFE technologies. If you take the pure ePTFE membrane, it is likely to be more breathable than either Gore-tex or Event. However, it will fall apart in your hands. Gore's basic patent for the ePTFE membrane expired a few of years ago, which is why a number of other manufacturers are able to offer ePTFE membranes.
Gore-tex and Event are laminate structures, using a face and inner scrim fabrics either side of the ePTFE membrane to support and protect the fragile ePTFE membrane (in 3-layer fabrics). Since a glue is needed to create this laminate, the result is less breathable than the pure ePTFE membrane, unsurprisingly.
If your 'military' information came from the DoD Natick labs, then my guess is that the pure ePTFE membrane is used as a reference point for the different ePTFE laminates.
Just to further confuse things, Gore use a thin PU coating on their ePTFE membrane to resist oil contamination. Event use a different oleophobic technology that allows their ePTFE membrane to remain air permeable.