While I agree with the principle you espouse, noting that “Snowden been documented as correct in everything he’s asserted so far” isn’t exactly calling him “a hero who can make no mistakes”. At this point, yes, Snowden’s claim is reasonably strong evidence in and of itself - because he’s proven a tendency not to make claims that he can’t back up.
In this case, Snowden’s making a claim that everyone in the field has been vaguely assuming was true for years, so he is the crosscheck here.
