I missed that part in the OP....and agree...that spring holds the butterfly centered in the venturi, and prevents it wearing grooves/gaps in the venturi and on the butterfly. Un-hooking the spring from the return arm is done frequently, but I don't think very many experienced guys remove the spring, except maybe the first time before they found out how come that's a bad idea. Erratic running, poor idle, inconsistent throttle all can occur within a short time of having that spring totally removed.

If anyone wants a "war story" about how I learned it, let me know, although it isn't very exciting.