Thank you very much for your question -- this is indeed a mistake/typo on our part. The correct values are the ones in the 8.2.1 Dimensions section.
Let me provide a bit of a background. The big difference (at least in my view) between the two sub-leagues (Lightweight vs. Open) is the ball they use (IR vs. Orange). That is also where the different ball capturing zones come from.
When you take the IR ball, its diameter is fixed at 74mm. A 3.0 cm ball capturing zone means that about 41% of the ball can be legally covered.
The orange balls on the other hand are smaller in diameter (65mm) and so if we left the ball capturing zone at 3.0 cm, it would mean that about 46% of the ball can be covered. That was deemed a bit too much, and so we now have the 2.5 cm ball capturing zone, which amounts to about 38% of the ball being covered.
Once again, I am sorry for the confusion this created. I also understand that having bigger ball capturing zone may simplify the robot design in many ways (especially since the ball capturing zones were the same for both leagues), but in the great scheme of things it should not be that problematic (please let me know if this is not the case).
I hope my explanation helped to shed some light on why these specific numbers have been chosen. If you have some more questions, please feel free to ask further -- that's what this forum is for after all =)