When a copper pour area is poured, gaps are left around items that are on different nets to the copper itself. The size of these gaps is determined by the Spacings on the Design Technology dialog, exactly as if you were adding the copper interactively yourself.
As well as the gaps between the copper and the items (determined by the Spacings), the linestyle width used for the Copper Pour area outline also determines where the Pour can 'reach'. In other words, making this outline thicker will mean there are larger gaps between the pads where the copper can't pour. Making it a smaller linestyle will mean it can pour into small 'gaps', and incidentally will also produce sharper corners.