jerry adams finally got the engineering, I believe he's the first person to actually discover what the differences are, or at least the first one to post the measurements that I've read.
For the record, some old 90s platypuses, the squarish ones, work perfectly. 2012/2011 era purchased ones do not work, but the key word is purchased, since there is no telling when REI actually received those bags from platy. All evernews work from what I read, and they are nicer bags anyway so to me it's a no brainer.
Same would go for 2013 purchased, if they are newly received, they should work according to reports, but if they were old inventory they could well not work.
And yes, the ones that leak do not just slightly leak, they are totally and utterly unusable, for the reasons that jerry noted, the threads are simply not compatible, no matter what you try with using different washers etc.
Nice to see someone actually figure out the difference in a measurable way though.
I am not surprised to see those bags popped when dropped, they are just not strong enough, that's self evident, though I did find a great use for the 1/2 liter bag, I cut the top part off and use it as a water scoop for the dirty water bag. Also wraps nicely around the sawyer so I can put it all in a nice little mesh stuff sack I made for it.