you are right, the lines in the middle has to build a cross, not a diamond.
Actually, any files with bleed elements in the middle of a double page will not get a right print.
I believe FFCore comes closer to what you are looking for when "resize pages when shifting to preserve content" is selected. However the inner sheets (pages 28 and 29) appear to have the lines cross over which I believe is incorrect. I believe all the sheets should appear like the outer sheet (pages 56 and 1). The inner pages should be scaled in the x-direction so that the lines in the middle form an "X" -- not a small diamond. Does this match your expectation?
I try to document it with some pictures. First I made tests with all the possible adjustments. I insert them in the following link. None of them is working in that way it has to be from my point of view.
The document "FreeFlow Core Job Creep.pdf" shows up the different results.
In my opinion is the main issue, that the zero point is not correct. For the job creep the trimbox at the collar is relevant. The acual behavior looks as the bleed at the collar will be used for the creep, with is wrong.
I am still not understanding the issue. The imposition is not scaling in the y-direction (top to bottom) for your WF. The points where the diagonal lines meet changes as the inner part pages are "cropped" for the specified creep.
What am I missing?
In this case, because it is a 4 page template you do not need to scale the hight of the page (y direction). If the template has folds in the x direction, the scale has to be there also.
no the inner pages has to be resized in the X dimention for example with a factor of 98.5 percent. In the middle of the pages the circle has to be closed. Of course it would not be a circle any more, but not in a visible manor.
And the lines must give their "hands" without a brig or a missing elements. Imagine that the page 28 and 29 in your example may be a panorama picture with a moutain. In the middle of the picture is the peak. You would not like loosing the peak or having a white stripe in the middle of it.
Is the expectation that the inner pages look like the below? With a white gap in-between the pages and the trim box contents maintained? I struggled with pain to make the picture -- which isn't the best.
you can see on the last pages of your PDF, that in the middle of pages tiles from the opposite page goes into the visible space from left to the right. Thats the problem I mentioned. If you scale the pages, they have to look in the middle the same as the outer pages. Otherwise your picture has a buckle in it.