What you’re missing is that the “closing lane” is often designed to be utilized to prevent traffic from backing up into another traffic control device.
While you’re “matching speed” with the open lane that’s hardly moving- traffic has now backed up into an intersection and caused gridlock on cross streets for miles behind you.
So while “total throughput” on YOUR journey has remained the same you may be causing chaos to the roads around you.
Your best bet is to just assume the traffic engineers who designed the closure know better than you.