No clip, I deleted that TOOL, remember?
The shackle supports the swivel. Anyone with half a gram of common sense knows what happens when a cord is wound without having any twist relief, that could surely result in some form of danger. Or at least a severely knotted, mangled, and unmanageable cord.
I am actually interested in this discussion and I don't believe I have been rude (as was accused by another, not you OneRestlessNative)
As far and the shackle and swivel, my cord doesn't seem to twist up. It is tied off to the webbing at the bottom of my SMB. I don't know if the way I reel up does not twist the line (unlikely) or if the SMB spins in the water to let the twist out (more likely).
FOR ME the bolt snap works better than my hand to wind up the cord. I am almost always doing this with thick gloves and often from considerable depth (70 to 100 ft). For the diving I do, I want to be a able to clip the boltsnap off to the reel at depth to hold that depth on a deco stop that may be a few minutes to over 30 minutes. Gripping the spool that entire time cramps up my hand, so I clip it off and rest my hand on top of the spool, line between my fingers. It is also pretty hard to switch to a deco bottle with your hands full of reel.
I have also dropped a spool. It goes all the way to the end of the line and if the line is not tied to the inside of the spool the spool keeps going. Mine was tied but it was a PITA to pull it up and rewind it all. So I do not like a spool that is not clipped off when I am not putting line on or off of it.
If these are not considerations for you, do it your way, but that is why we (the tech divers that answered up) do it the way we do.
On a serious note about the octo keepers, the snorkle keepers are great if you are donating the octo in a OOA situation. It is what I used when I did it that way, and I use snorkle keepers on my deco bottles to keep the reg where it should be.
If you get a chance to try a long hose with the octo/backup on a neckless I think you will really like it. Sounds like you are practicing skills on your dives alot and that is great, so evaluate the "long hose" configuration for yourself during an air share drill. I tried it once after diving the other way for 22 years and I love it. It makes alot of other things you may have to do while sharing much more managable. PM me if you want any non-judgemental input on what to try. I can give you a octo neckless that I used before I went to the bungied style. The rubber neckless might be nice if you are diving without a hood.
If there are other questions you think someone should address, tell me that they are and I will try to give some kind of unbias answer.