This would depend entirely upon what is stated in the works information specific to that contract.
The short contract does not anticipate the Contractor doing (much) design and so has :
no provisions for “Contractor’s Works Information for his design” as per the ECC; and
no requirement to submit designs for the Employer’s acceptance< so a Defect is NOT “a part of the works not in accordance with the Contractor’s design which the Project Manager has accepted.” (see the definition of a Defect / clause 11.2(5) of the ECC.
Consequently, providing what the Contractor builds complies with the (Employer’s) Works Information and applicable law, they can build what they like and if the Employer does not lie it, they need to change the Works Information which is a compensation event.