An exhaustee who desires to claim extended duration benefits shall file a valid primary claim. A primary claim for extended duration benefits shall be valid only if its effective date is within an extended benefit period and the individual filing it is an unemployed exhaustee. For the purpose of determining whether a primary claim is a “valid primary claim” within the meaning of this section, an individual otherwise unemployed shall be deemed unemployed even though wages, as defined in Section 1252, which are for a period subsequent to the termination of performance of services are payable with respect to the week for which the individual files the claim.