For any form dimension longer than 1500 mm, auto-center along the long axes is overridden in both the Print dialog and the Print Organizer previews. That is, the preview does not display the entire form on the long axis. Rather, the form preview is clipped to include only the plot origin and plot size.

Example:

36" form width, with the 22" plot Y size centered within that. 105" form length, with the plot origin set back 2" along that direction. Print preview is trimmed along the length, but not the width: