well, okay. But with my 40 posts and your 100s I'd have thought I'm the neophyte here and hardly presume I could teach you anything but here goes. Bear in mind I'm not a guru because I'm too lazy to keep head in books.
To my knowledge (or lack of) The ETOPS threshold is calculated at
a point 60 minutes flying time from an adequate airport at the selected one-engine out diversion speed schedule in still air and ISA conditions. The reference for this particular definition is found, I think, in FAA AC 120-42A but is good enough for the local case.
Note the still air reference and also
selected speed. I guess if winds were taken into account for these calculations on a case by case basis it would confuse us (the drivers/pilots/cockpit crew... anything but b***y "tech" crew).
Also it is a sensitive issue, this flying around on one engine and obviously forecast winds would have to be used at the planning stage which is not good enough.
And now back to moaning about puerile issues.........
.