Because they now have an operating production line and processes?
They don't. The KC-767 Tanker supplied to Japan, and almost supplied to Italy is not the same as the KC-767AT on the USAF bid (for one thing B has to tweak the design to lift ans extra 40,000lb jet fuel)
If Boeing has used the 6 month grace period to have its design staff do actual work on the design, it may have a chance of meeting the original schedule.
If, as I suspect, that was mothballed while Boeing management talked to its Senators, there won't be any Boeing Advanced Tankers built before 2015.
Your suspicions are probably valid, typical solution would be to throw people (bucks) at the problems as soon as funding is reasonably assured.
The six months in question were not likely happy times for BAC engineers.
Remember also that they are funding, or have funded, a good bit of C-17 production on their own nickle pending USG actions and might not be over eager to risk more shareholder assets.