I'm dead certain it is for Win7 upgrades, since those upgrading from Win8.x wouldn't have the issue (or would have had it some time ago when they initially got Win8.x)

It only became a problem...

Hi dashbois - frustrating innit :(....
From my research I reckon the issue is probably (possibly) only present with older APs which only support WPA-TKIP, which I understand was removed from Win8...

This is probably teaching people to suck eggs, but may help clear things up for some readers...

I was unable to connect to an older (backup) AP in Win10, but Win7 and my phone, tablet etc could...