I read your article with great interest, because bouldering is my favorite sport to shoot. One of the reasons is, that it is so easy to shoot and allows you to be so creative with different angles and light setups. So what you say about flashes might be true if you need as many good shots as possible when shooting an event or for stock.
But when I go out I don’t need 15 good shots, in general I’m happy with the one that turned out exactly as I wanted. And in this case would say it is so worth it to have a second look at the scenery and setup a reflector (never forget the reflector or a flash to highlight a little detail.
Flashes don’t have to be seen on the shot. Quit often it is better if you don’t know if there was a flash used or not.
In this shot for example : http://500px.com/photo/15985797 a reflector was used to brighten the rock a bit and a flash to the left of the climber behind the flowers to separate her a bit mor from the rock.
Or in this one: http://500px.com/photo/3047289, a flash was used to brighten the scene from the same direction as the sun, which was shining though the woods, but the boulder was in the shade.

So all I wanted to say was pay attention to the details! And super often you can enhance a shot by using a strobe to get a little catch light on a mushroom in the foreground or something like that…

So let me know what you guys think about that…

Aloha