I am totally confused here...

The mount you showed you liked leaves a portion of the mount on the rail at all times. You just undo the QD portion and remove that and leave the base affixed to the rail.

SO, this one, like that one, is affixed to the rail at all times. BUT it is 1 step better as there are no moving parts to remove. You just unclip the sling and your done. No extra dangling piece.

So no, you do not in any way have to remove the mount to ditch the sling. Nor do you loose the ability to go from single to double sling.

I have a sling, my rifles have a mount at the buffer tube. I click my sling into that and now.. I am 1 point sling. OR, I can click into this mount up at the rail and I am now 2 point. Not lost anything, not removing any part of the mount.

I think this is more coming down to the type of sling setup you have and not so much about these 2 mounts as I can do what I just said with my sling and loose nothing and take nothing off and can go 1 or 2 point. I think you have the QD swivel(s) attached hanging from your slings whereas I use HK snap hooks on my slings.