Who is right?
Technically you are both wrong. The contractor is entitled to assess the compensation event based upon the effect the compensation event is forecast to have on its defined cost, see clause 63.1. But the contractor can only recover the increase in cost of any material that was caused directly by the compensation event. This will of course depend upon how and when the contractor procures its material.
For example, did the contractor procure the material on a fixed-price basis or a price subject to cost increases, and did that procurement happen at the beginning of the contract or later? It is for the contractor to justify the increase in its costs, and it should supply you with more information on the issue for you to make a decision.