I forgot to add in my first post, the clip on the long hose is so you can clip it to your d ring, if your doffing using the necklace clip it off. I use it gearing up and when I get out of water.
Not trying to be argumentative, just using your post as an example, I don't believe my way is the absolute way to do things, but here is some of my thoughts:
Typically when one uses long hose setup their octo is on a short hose and hung on a bungee or other type of necklace to stow it between their chin and chest area depending on how small the necklace is made. The low pressure hose is typically between 22 and 26 inches long. The long hose, is recommended to have a bolt snap attached so it can be clipped off before and after the dive so the primary 2nd stage does not hit or drag on the ground. The bolt snap can be used but is not typically meant to be used to clip of the primary 2nd stage during a dive unless one has a 2nd stage issue and switches to their octo for the remainder of the dive, be that an immediate ascent to the surface or after consideration of all factors to continue the dive. Otherwise the primary 2nd stage would either be in the wearer's mouth or the mouth of someone they are sharing their air source with.
If one is only doffing/donning their gear as a matter demonstrating the skill then swapping to the octo for the duration is plausible but beyond just taking one's rig off and immediately putting it back on then that short 22 to 26 inch hose does not give one much length to really manipulate their rig and inspect things. Not sure why one would do this when they can do it comfortably with the 2nd stage with the long hose in their mouth.
In my previous response I mentioned I would pull my primary 2nd stage out and switch to my octo before pulling off the necklace. The reality is that I would only do that if demonstrating for educational purposes. In actuality I would just pop my primary out of my mouth with one hand and reach back and remove the necklace with the other then pop my primary back in my mouth with the hand it is being held with. The timeframe my 2nd stage is out of my mouth is only 1 to 3 seconds and I can blow bubbles for that long without problems. During the maneuver I can always stick my primary back in my mouth or stick the octo in my mouth should that need arise.
It was recommended me, when I first started diving a long hose configuration to attach my bolt snap to the hose far enough away from the 2nd stage so that one can put the 2nd stage in their mouth and breath off it while it is clipped off (just in case one forgets to unclip it for some reason before splashing...never happened to me and the only time I can see this happening is if one does their buddy check before walking to the water's edge for a beach type entry and then enters the water without unclipping their 2nd stage, this apparently has happened enough that there is a recommendation for where the bolt snap is attached).
-Z