NEC4 Option A - Priced with a BoQ

I have recently come across an NEC4 Option A contract where the price was established using a “pricing schedule” (effectively a BoQ, the client issued the quantities to complete the works and Contractors entered rates for each line item). The “pricing document” was converted into an Activity Schedule. The Contractor had an item of “152m3 of C30 concrete to be poured” in the contract Activity Schedule, they have ended up using 182m3 on site. The Contractor is trying to claim the extra over (30m3) is a change and a CE, but the contract has not been amended to reflect this.

Cl55.1 states “The Activity schedule is not Scope or Site Information”. I can’t see a way the Contractor can persue this as a CE? I think a mistake was made in the drafting of the contract and in essence the extra over has become the Contractors risk by default. To prevent this the contractor could has stated in the Scope "The Price Schedule/Activity Schedule is deemed to be Scope, changes to the stated quantities would form a change to the scope (hence a CE Cl.60.1.(1)). Or the stated quantities could have been included as an additional Clients Liability (Cl.80). As none of the above was included in the contract wording, is there any other recovery method for the extra over? or does the Contractor have to complete that element of works at a loss?