I would think that ICO would deplete the fuel piping of fuel, so it would take longer to get the engine delivering power, than if one closed the throttle.
I don't think so. The mixture control cuts off the fuel pretty close to the injectors/carb, so I doubt there's a time issue.
interestingly, it looks as though posters are divided on this one?
I don't think there's much division on the practice. While I'm happy to examine the pros and cons in the spirit of debate, I can't find much support for using the mixture control on an SEP.
MEP debate and
another.
Schiff's view
FAA advice
SEP Accident and
MEP accident