Looks like your method worked out a lot better. I don't use the face to face loft much, mainly because it doesn't allow guide curves, so it's not in my train of thought when working on lofts.To best describe it I wanted to use the face to face loft but it doesn't work for me when the 2 faces share and edge and especially not for 3 faces. So I made a grove cut to separate the faces. Then later filled it in and removed any excess.
The best as I could get your original using those settings: it needed to be -90° for the top's tangent setting which also made "love handles" on the sides of the rectangle which were unwanted. Potentially/maybe/with some tweaking - it could have been done that way and then chopped off the extra but I wasn't happy with the shape. As far as I can tell it's 100% trial and error getting the magnitude right. I will say this adventure makes me more aware of how badly Alibre needs to fix the error dialogs when previewing.In the loft dialog, what does the tangent angle setting do? I expected that since the tangent it produced was 90 degrees from what I wanted, I could change that setting to 90, but that doesn't help. And the magnitude setting makes even less sense to me. Varying it usually didn't show a change or pupped up an error.