The financial model can often be the last thing to get signed off before a financial close because as time goes by (eg waiting for other CPs like EPA approval) there can be a tendency for it to be tweaked with / refined, either because new info has come to light that would make it more accurate (eg the SOP price may have changed since the first iteration) or because the lenders think of some further sensitivities to be performed. I've often been the one asking for further tweaks to models whilst waiting for other loose ends to get tied down...
I imagine that if EPA approval had been achieved the model would have been signed off by now.
You're right that the truth will only really be known once the plant's up and running, but everyone needs a model to base their investment papers on and to run covenant tests on etc. The idea with the base case model is to make it very conservative, with theoretically very little chance of it not being met.
SO4 Price at posting:
56.5¢ Sentiment: Buy Disclosure: Held