Haven't tried the native Max, but I did this - took a bitmap, put it through two Corona Color Corrects, one using Invert, one using the "reversed curve". I then screengrabbed, copy-pasted into Photoshop, duplicated, and inverted the duplicate there. The Corona Color Correct invert, once inverted again in Photoshop, matches the original (and the Photoshop Invert matches the Corona Color Correct invert).
The Corona Color Correct curve change, however, looks very different from the Photoshop invert result. So, to me, it looks like the Invert in the Corona Color Correct is working as expected, and either there's a problem with the curve, or there's just a misunderstanding as to what the curve does. As to what Max native invert is doing, not sure :)