IGI only has incidental death/burial records (and these should never be relied on) thus you get baptism (not birth) + marriage records.

The Manx records based on the microfilming of the 1911 official copy of parish registers was one of the first areas to be transcribed - those indicated as extracted are generally very accurate - however when the IGI went online (away from the old microfiche) SLC for some strange reason replaced many extracted entries with patron submitted entries + many 'new' entries - patron submitted entries generally have a very high error rate (at least in double figures)