I'd say it was a couple microbeats early.
I'll put it this way. If an official had thrown a flag, Kramer would have had no course to complain about a bad call.
It may have been done thousands of times on other plays, but those thousand or so plays haven't been discussed and analyzed like this one.
Impossible to say what impact it had. Kramer was on Pugh before he could get out of his stance...for obvious reasons. Nobody will ever know whether Pugh could have stayed low if Kramer hadn't beaten the snap.
Kramer never really denied this, from what I understand. I think he admitted it in his book Instant Replay.