What deep point am I missing beyond that?
That Libby lied to the GJ. What he told Russert is irrelevant - he could come into the GJ and say "I lied to Russert," and he'd be fine.
But several reporters say they learned of Plame from Libby - Libby says he learened of Plame from reporters, and independent notes indicate that Libby knew of Plame before he talked to reporters.