The previous advice is correct in that they are not AUTOMATICALLY Defects.
However, as a Defect is a part of the works not in accordance with the Works Information, then any incomplete work - from the time of signing the contract ! - would satisfy that definition.
Consequently, as you conclude, once enough work has been done to achieve Completion (whether as per the contract clause or by reference to the Works Information), once an item of incomplete work is notified, the Contractor has the defects correction period to correct it.
However, as a Defect is a part of the works not in accordance with the Works Information, then any incomplete work - from the time of signing the contract ! - would satisfy that definition.
Consequently, as you conclude, once enough work has been done to achieve Completion (whether as per the contract clause or by reference to the Works Information), once an item of incomplete work is notified, the Contractor has the defects correction period to correct it.