All chain, sealed or not is shagged at 2% elongation, on most bikes around 1.5".
Not rocket science just all chain has 2% case hardening, any more you get brittle pins
and any less poor wear. Hint you also get poor wear with crap steel regardless of
case hardening. Also on budget product the hardening may not be even.
After this you are on the soft stuff. With non sealed chain it lets you know, problem
with sealed chain is that the seals make it difficult to test so you have to dismantle
and mic the pins. I have seen some sealed chains 5-6 times over the wear limit.
To avoid this some modern bikes have a marker on the swinging arm showing when
to change chain and it is nowhere near full adjustment.
On the thorny subject of O ring etc, I have always said the power loss is a small % but
when you have low power machines a small % makes a difference 1.5% of a 100hp means
feck all 1.5% on a 20hp will show.
I will wait for the court papers
Andy