"My Platy was purchased in spring, 2010. It's possible that Dale has an older or newer Platy, and the threads changed slightly at some point."
And/or Sawyer has some variations in tolerances too, just to make this all fun.
I tried several Platys, one that is a couple weeks old to me, but who knows how long it was on the shelf. The rest are from a span of years. All are pretty much the same threads except that 34oz Platy "SoftBottle" that has thinner threads (and still doesn't work).
My filter has a white washer too. Looks just like a garden hose washer. It makes me feel very special.
I'm pretty good mechanically-- automobiles, cars, bikes, boats, appliances and plumbing, and when I tighten a Platy into the filter, it seats at a distinct angle and does not feel right when it starts to tighten down. Every mechanic fiber in my being says "STOP, IT WILL STRIP."
Like many things, you could make it work, but I think it would get damaged with use, and when you let all the "use" out, it becomes "useless." :)
The Platy on a Sawyer, note the "unnatural" angle:
the Sawyer bag on the Sawyer filter and all right with the world: