I think that the overall stats are flavored by the outside competition you play, and are less accurate as a comparison measure. That is why I prefer to look at the BIG stats only.These percentages are for field goal percentage (in conference games only), rather than points per possession. Purdue did really well in this category.
Once playing inside the BIG conference, most teams had fairly equal schedules. Those claiming this or that school had "easier" schedules are generally talking small fractions of difference across a full 18 game schedule, specifically when dealing with the statistical measures.
When you talk defense and offense, that field goal percent is a reasonable measure to compare any two teams on their relative capability. What this says is that while Indiana lead the BIG in scoring, they were about as efficient as Purdue on offense, but defensively, they lacked much, ranking dead last in the conference.