Rationale:

Not a defect. The LWG believes that the Standard is already clear, and that the above summary is what the Standard in effect says.

Table 88, in I/O, is too strict; it's unimplementable on systems where a file position isn't just an offset. It also never says just what fpos<> is really supposed to be. [Here's my summary, which Jerry agrees is more or less accurate. "I think I now know what the class really is, at this point: it's a magic cookie that encapsulates an mbstate_t and a file position (possibly represented as an fpos_t), it has syntactic support for pointer-like arithmetic, and implementors are required to have real, not just syntactic, support for arithmetic." This isn't standardese, of course.]