Levy is concerned about the public infrastructure and the various local partners living up to their end of the bargain because this reassurance is needed for the banks, not just for the stadium but the entire Northumberland Development Project. The stadium by all accounts is on schedule, perhaps a bit ahead since they were able to start on the 6th core when they demolished the northeast corner of WHL.I think it's pretty obvious that it (or other elements involved) isn't or we wouldn't be keeping the option open of deferring the PC date of the stadium build.
Levy is trying to put additional pressure on the council and other public partners with this language - there is no advantage at staying at WHL another year as the south stand, sliding pitch, and roof cannot be started until WHL is demolished, not to mention the NFL deal that stipulates a 2018 start date to the agreement. The FA is also playing along by letting the decision slide into April to give Levy additional time to get everything aligned before moving forward.