Earlier this year I acquired a second-hand Cannondale Trigger 2014, that was used just twice but standing around for quite some time. Today I wanted to change some things about the cockpit and as a part of it, tried to remove the grips. Not having seen any "sophisticated" end plugs ever I just untighted all screws and then tried to pull the grips and endcaps free - no luck. With admittedly few thoughts I kept turning the middle screw and managed to get it out all the way. Only later did I realize I probably shouldn't have done that. I can clearly hear the counterpart moving inside the handlebar. On the second grip I tried to do it right, but that just results in the middle screw being loose, the counterpart still being connected, but it's still mysterious how to get the entire plug out. The screw is the only thing I can pull on, but that just pulls in the counterpart and expands the plug, i.e. getting it stuck even more.
I can't find any specific details online or in the manual about this handlebar plug/cap or even any instructions, how to "normally" remove those types of plugs. I know options to remove them destructively, so that's not what I am looking for.
In "normal operation", how would you remove this handlebar end plug?