its not about what's on the box. if you read the thread i posted there, lots of games have "misprints". that thread is about tried and tested games that definitely do NOT support 1080i no matter what you do to them.
soul calibur 4, for example, only says 720p but it supports 1080i. the LBP beta i tested myself and it doesn't support 1080i. games like top spin 3 say 1080i/p on the box, but do not support it in game
so basically, what it says on the box is not necessarily the truth.