NEC3 ECC: Schedule of cost components - people outside the Working Areas

Under an ECC Option C are the costs of people who occasionally work from a head office recoverable as Defined Cost for the period they are not within the Working Areas? Even if they are providing the works during this period?

The Schedule of cost components splits people down into three categories;

directly employed and whose normal place of working is within the Working Areas,

directly employed and whose normal place of working is not within the Working Areas but who are working in the Working Areas,

and people who are not directly employed but are paid for according to the time worked while they are within the Working Areas

Items 11, 12 & 13 then set out the components that are recoverable under People. Item 11 states:
 
11    Wages, salaries and amounts paid by the Subcontractor for people paid according to the time worked while they are within the Working Areas.

Does this mean that someone whose normal place of work is within the Working Area, and who is Providing the Works but for 1 day each month this is done from a head office, would not be recoverable for this day as for this day they are not paid according to the time worked while they are within the Working Areas?

If the answer is no, what is the purpose of the distinction between people who are directly employed and whose normal place of working is within the Working Areas, and people who are directly employed and whose normal place of working is not within the Working Areas but who are working in the Working Areas?