Main stat difference for similar ilvl

https://www.warcraftlogs.com/reports/compare/mW74rp9vZb1MBXz3/mW74rp9vZb1MBXz3#fight=43,43&source=65,18

There is a 10k difference at Intellect, although when I added up the intellect from gear, it should be a 3k difference the other way. What am I missing? If the displayed difference is correct, where does it come from? Could use some help

Stats are snapshotted on pull, so he probably rolled into the pull with buffs up already.