As of now, three relatively small agencies require horizontal trim and no silting for their students in OW: GUE, NASE, and RAID. They require it not for 60 or 90 seconds, but for the entire dive. NASE requires that you be able to stop, turn and start again without changing depth and not using your hands. I never taught for the other two agencies, so I can't comment on them.
I have seen cultural change amongst divers here on SB as well as in the field. Uncle Pug and Roark were the lone sirens calling out the "roto-tillers" as UP called them. It was kind of tiring. By the time I hit my NAUI ITC (Instructor Training Class) I was as neutral as it got which led to utter humiliation at times. We were doing final presentations in King Spring, and the silt on the bottom was EPIC. But I was taught to teach my students on their knees in the pool as a control technique. If you wanted a five you made sure they were planted on the bottom. Not being an ounce overweighted, I couldn't plant myself. Suffice it to say, that the silt didn't stay on the bottom. I was allowed a do-over in an even siltier lake, fortunately with an elevated platform. During the debriefing, the ITs argued that there was really no requirement to kneel, so I could "theoretically" teach off the bottom. The Course Director but kibosh on that pretty quick. Needless to say, I always went in at least five pounds heavier than I needed after that. I did the same to my students so I could plant them on the bottom as well. I didn't like it then, and it was the impetus for me to figure out how to get off the bottom and get them neutral. It's nice to see that some of the harshest critics from my early days of trial and error, now advocate for teaching off of the knees.
The King Spring debacle will almost always be one of the lowest of lows in my teaching career. Luckily, nothing takes the sour taste of shame and humiliation out your mouth like Be-Bop-a-Re-Bop, Rhubarb Pie. (I played this a lot during that ITC)
