I know I have never taught anything, never having been an instructor. I still feel it is logical to say it is at least somewhat harder for some students to be taught skills neutrally from the get go. Not saying I disagree with it being taught that way at all--I did see an improvement in students on checkout dive 1 in my last year assisting (2015) when more time was spent basically hovering around in the pool (not necessarily while skills took place).
But, here is a quote from someone who HAS experience-- Lynn Laymon, Aug. 2015 article in Dive Training mag.---
"WORD OF CAUTION"
"Removing and replacing the scuba unit is significantly easier when performed while standing on a solid surface, like the bottom of a pool, lake or quarry floor. That is fine for learning the skill and practice. ....., once you become comfortable...try executing it midwater. ..... Be prepared to adjust buoyancy. ... Depending on the type of weighting system you are using, the scuba unit may float up as you sink or vice-versa.....This can be dangerous.....It is important to maintain secure physical contact with the unit and to keep the combination of the scuba unit and your body neutrally buoyant throughout the skill"
Now, removing & replacing the unit was always my worst skill and it actually held up my DM certification.
But in reading this article, logic tells me its harder to do this than to plant yourself on the bottom, particularly if your total prior water experience has been in the shallow end of motel pools on vacation.
Other skills, such as mask clearing, reg retrieval, etc., would seem to be a whole lot easier to do neutrally the first time. In fact, in my own diving and assisting, I have done these on my own and while demonstrating to students very well the first time, without any prior practice doing them neutrally.
My final conclusion from all those other threads was that the reason teaching the skills that can be done neutrally neutral (not that many-- 7 or 8?), is not the main reason students are much better divers after certification (or even on the first checkout dive). I figure it is the fact that while one student does a skill in the pool everyone else is hovering looking at him/her, and not wasting time kneeling on the bottom. That's a lot of neutral prctice.