why though? in particular if the NSA wanted to hide their nefarious intent here, why wouldn't they use something stronger than an LCG so the question for how they're generated remained open forever?

What's more likely, the random calls were made at those times, or that someone changed the numbers to make it look like they were made at those times?

Only one of those requires a conspiracy theory-tainted brain to think up.

it would have been beneficial to disclose the origin.

lying for obfuscation purposes makes zero sense given what we know now.