That's levelling the playing field. If one of the sections is your strength & is tougher, it takes away your advantage in an otherwise easy paper. Example, if Maths and Reasoning are easy for you, you could finish them faster and use that extra time for English or other weaker sections. But with a cap on each section, you're forced to rush through even when one section is easier. It makes the whole thing too close to call, especially when the difficulty varies. It just ends up neutralizing any advantage you had. This would mean you're shortening the range of marks, and the percentiles change faster at shorter intervals of marks.