Well, there are different opinions, and there are different aspects involved. If you read some works of Dr. Joulia, or Seb Murat, and others, they indeed do think that the DR wears out, better told it gets harder and harder to kick it in. In the same time, regular wet training helps stabilizing the DR, and to pull more out of it (for example by having higher lactic tolerance). Dr. Joulia worked with Steph Mifsud when he prepared his STA WR (11'35"), and the training was in bigger part dry, exactly for the reason of avoding the loss of diving response.
So on one hand you have athletes who try preserving the DR by avoiding exploiting it too much. They train a lot dry, or when they train wet, they avoid no-warm-up and preserve this shock-induced DR for competitions only. On the other hand I know very sucessful freedivers who start all their trainings with no-warm-up max attemps. And from what Dave wrote, it looks like he belongs rather to the second group than to the first one.
The conclusion is that you can likely become a top freediver in both ways. Whether one way is better than the other is hard to tell, but at this moment it does not look like there is any important difference.