I dont think that anyone would say that watching around or looking up is more comfortable, natural or practical in an horizontal position. And it easier and less stressful on the neck sometimes. In my view, learning to be neutral in an upright position is almost as important as in an horizontal one and we should not criticize divers clearing their masks, launching their DSMB or doing their safety stops vertically if they don’t disturb the environment. That was really my only point.
And nobody in this thread has disagreed with your point. Nobody in that
previous thread from a year and a half ago about this topic disagreed with that point, either. (And yet, the person who started that thread similarly was under the impression that there is some persistent inflexible dogma about "perfect horizontal trim" floating about SB and perhaps elsewhere.)
Back in 01/02, when DIR was in it's heyday, a couple of their acolytes used to promote this. They even asserted that you off gassed better while prone. Physics and physiology won out in the end. I don't think anyone still believes that you have to stay horizontal all the time anymore, though we are often portrayed as asserting just that.
I can only imagine. Way before my time. All I know is that none of my GUE instructors in the past 8 years have told me that I must remain in horizontal trim all the time on a dive. On the contrary, as you know, it's a necessary skill to be able follow the contours of a cave as the passages go up and down. But I have to admit, the skill of being in horizontal trim is so drilled into us in our courses that in some situations we forget it's okay, even preferable, to do something else. For some time after our original Fundies course my wife would try to descend from the surface in horizontal trim, until an instructor advised her to stay vertical until her head was underwater, THEN slide into horizontal trim, to better help vent the drysuit. I had told her I thought that was common sense, but she wouldn't listen to me until the instructor told her it was okay.
I might not find one right away but you have to admit that there is a lot of sentences like good trim is horizontal, all the skills should be taught and performed horizontally… on SB.
You (and others, such as the person who started that earlier thread) may be taking those "sentences" out of context. We need to keep in mind that when someone writes a statement like that on a forum like this in a thread discussing the benefits of horizontal trim, the person rarely takes the time to write all the caveats, exceptions, considerations, etc., along with the statement.
"All the skills" are
taught horizontally
in a course because making things more difficult than they might be in the real world--making the student work harder than might be necessary--is good training and helps build muscle memory. It's good for a diver to develop the muscle memory to perform the skills horizontally. When I practice the skills, I do them horizontally. On a real dive, horizontal may very well be the best position for doing certain things. Nevertheless, on a real dive, if the diver believes doing something in some position other than horizontal is preferable for whatever reason, the diver should do it that way. As I said in an earlier post, I wish this were explicitly mentioned in class. It may be that instructors think it's common sense and don't bother mentioning it.