So.... can we say that the clam digging has "ended"?
We can at least say that it appears to have ended for now:

I guessed he had around 517k CLAMs to dig. The chart shows a little less than 500k being dug since he started, so my estimate may have been a hair on the high side:
Checking my clam logs, I see something strange about the recent 'digging':
So it looks like this guy, whoever he is, is able to claim around 3.5% of the rewards in each block, and is working his way backwards through the blocks. According to xploited, the initial distribution ordered the rewards randomly, so there's no reason to think that he won't be able to claim a similar percentage of the rewards from all the blocks.
3.5% of the initial distribution means around 517k CLAMs. In which case this digging spree is only just getting started.