I must say that I tend to read the rules the same way as UserMark. It does seem to be quite explicitly the "free" segments where you are limited to two long ones, so as I read it you could purchase, say LHR-DXB-LHR in addition to LHR-CAI-LHR on a xONEn for US$1100/GBP700 in F, provided that you abide by all the other restrictions (which still limits stopovers to 2 if your continent of origin is Europe). On an AONE3 originating outside Europe there seems to be little downside to this when ba.com quotes GBP1634 (including taxes) for the same two segments.