I imagine it was difficult to predict how much they'd be able to...

I imagine it was difficult to predict how much they'd be able to raise and at what price once the ALB bid was withdrawn, and they didn't want to put downward pressure on the SP by pricing it too low. By raising more debt that they need (which I assume is just drawn down as required) it gives them an insurance policy in case the equity raise is too difficult, the thinking being that if there aren't enough takers at the $2.20 - $2.60 asking price they can just fall back on the commercial/government financing and they're still covered to production