(T2T, I can't believe you remember I was going on about that!)
This is how I see it: they planned on releasing the Feasbility with old RE numbers. Afterwards they planned on releasing the RE2.
Then they were handed a delay by TT. It was unexpected, I think that was clear. When they were told about the delay they realized they were close to finishing the RE2 and that it was going to be substantially better than the first one.
At that point, they decided to a major delay in the feasibility so that they could incorporate the RE2 results. This would presumably make the whole project so much better that it was worth the further six months delay (or whatever it was.) They brought in Jim Gray as well to ensure they had the best mine plan and the best project possible.
Also, the delay to get the RE2 incorporated into the feasibility makes the feasibility document and included mine pit plan, etc., one that can be used to actually begin building the mine. This, in my estimation, makes the project far more valuable to Teck/whomever because it is primed and ready to go.