So this was never released in full-screen for blu-ray? No option whatsoever?
Nope. Just the Imax shots appear in full screen. Unlike DVD's, I don't think there's an option in purchasing BD's in fullscreen or widescreen. You get exclusively what the director intended for you to see. They call the shots when it comes to aspect ratios.
I prefer widescreen myself tho, just feels like a richer cinematic experience for me personally.