The Contractor should be showing the actual progress achieved and the effect upon the remaining work. If they have taken a punt and started something early before acceptance, then that is what they need to show. It is a risk, as if it end up being rejected then the work they have done may then change and actually show a delay rather than finishing early. So be it though, and at that point they show what they then know.
Quite a risk obviously for them to start without acceptance, but not a reason to reject I suggest unless they know what has been started early will be rejected and therefore not realistic. As you say if they did reject but that is what the Contractor has done anyway you will get to a point where they will never accept but the works will (have to) be proceeding anyway.
Quite a risk obviously for them to start without acceptance, but not a reason to reject I suggest unless they know what has been started early will be rejected and therefore not realistic. As you say if they did reject but that is what the Contractor has done anyway you will get to a point where they will never accept but the works will (have to) be proceeding anyway.