It would makes sense for the extra time and other information be pulled through to the Candidate Arrangement section. It takes a long time to go through each candidate in the year who is on the SEN register and duplicate the information in the Internal Exams Manager. It also relies on the person administering the exams being told of every small change (often at short notice).
Access Arrangements functionality is currently being rewritten and should be ready for release once the summer exam series is complete.