i think that Dan and Carla are not necessarily saying mutually exclusive things:
-You do not NEED to be an "advanced" freediver to be a world class spearo
-Being an "advanced" freediver will not hurt your ability to be a world class spearo, it will only help
both of these statements are the crux of your positions and they are both hard to disagree with.
-you DO NOT need to be an "advanced" freediver to spear big fish or small fish well....also true.
I think that Carla makes a very good point about the ability to dive deep making it easier to dive shallow and then expand your focus into hunting..makes sense.
a lot of the reason spearos do their shooting in 100ft or less is probably as much a function of efficiency as anything else...it takes a long time to dive to 100 ft and back up, why do it if there are fish shallower?