I have created a simple 2 page document in InDesign CS5.5, used style sheet mapping to tags, setup articles and used Object Export Options to set Alt and Tagged PDF information. Using Export, I create a PDF with Tags, bookmarks, and Fast Web view checked on. The produced PDF contains an Order definition in the Order pane. If I use Tools/Pages/ Replace/ in Acrobat X the order information is lost. If I open the Pages panel and use the same documents with drag and dropping the page in, the order is preserved. Is this appropriate behavior?
It's arguable as to whether it's a good idea or not, but that's how the Replace Pages system works and always has - it brings in a flat page with no tags, form fields, scripts, etc. even if those elements were present in the source document.
Ok, so Forms backgrounds are really going to need some re-thinking is they are intended to be fully supported for clients.