Dropped 3rd strike

[TriggerMN]

Runner on third, one out. Batter swings and misses at strike three, which is dropped. The batter takes four steps towards his dugout, and then realizes the ball was dropped. He then starts to run to 1st base. I call him out as he begins to run, because in my judgement, he had given himself up by heading back to the dugout.

Now the fun part. If I'm reading the rule correctly, 7.4.1 says the batter can run AT ANY POINT as long as he remains in live ball territory. However, at our state rules meeting in March, I could swear that the clinician there said once he gives himself up, he's out (somebody had asked about the play during the meeting). A couple of my fellow umpires seem to remember him going over this as well.

Could someone please verify the correct ruling here for me? And what do you do in this situation, where the rulebook says one thing, but the state clinician tells you another?

Also, doesn't it seem odd that the batter would be allowed to walk all the way back to his dugout, even to the end of the dugout closest to the 1st base bag, and THEN take off for first? Is there a good reason for this?