This might be a good approach if you're aiming to get the fibre/resin ratio as close to optimal as possible, but it will likely increase the possibility of seeing dry spots, especially on larger parts.  Allowing a little more resin in after closing the vacuum is the common approach to ensuring a complete wet-out of parts and any richness of resin would be minimal overall and likely not evident without using hi-tech measuring kit 

I'm not certain how positively closing the vacuum port later than the inlet port will affect the overall consolidation of the part either, as once the resin has almost completely infused, the effect of the open vacuum port appears limited to the area quite close to it. This is evident if you ever see a slight leak close to the inlet side just prior to a complete infusion, as air will not move quickly towards the open vacuum port unless the bag is pulled-up a little to overcome the already infused areas filled with resin. It's likely that the area close to the inlet will remain much looser either way, until the pressures have had time to equalise over a period of time during cure.