Yes and I fully agree with you. I am just being pedantic about this point:

I can only update my beliefs based on the evidence I do have, not on the evidence I lack.

I agree with this philosophy, but my argument is that the following is evidence we do not have:

Due to Snowden and other leakers, we actually know what NSA's cutting-edge strategies involve[...]

Since I have little confidence that, if the NSA had advanced tech, Snowden would have disclosed it; the absence of this evidence should be treated as quite weak evidence of absence and therefore I wouldn't update my belief about the NSA's supposed advanced technical knowledge based on Snowden.

I agree that it has a low probability for the other reasons you say, though. (And also that people who think setting other peoples' mousetraps on fire is a legitimate tactic might not simultaneously be passionate about designing the perfect mousetrap.)

Sorry for not being clear about the argument I was making.