Anyone see a game changer here?

It's kind of a stretch to go calling it "western propaganda" just because
one cybersecurity expert "is not sure".

If another cybersecurity expert suggested that it seemed possible that
little green men might be responsible for the attacks, would you suddenly
believe in Martians?

There is almost always someone who will take up an opposing point of view.
It's certainly good to keep in mind that there's a margin for error in
these sorts of things. However, it's also smart to keep in mind that a
large number of people have looked at this issue, most certainly including
a slew of experts from the government, who would have had to agree with
the China assessment prior to the State Department decision to issue a
formal protest.

... JG