Yes it is appropriate - and again an example of why it is essential for a Contractor to demonstrate both "planned Completion" and "Completion Date" on a programme. If the Contractor was performing well and they were already three weeks ahead on teh critical path then planned Completion would be three weeks early.
If there was then a compensation event that then required an additional 2.5 weeks of work on the critical path, planned Completion would move by 2.5 weeks but so would Completion Date move by 2.5 weeks (see NEC3 ECC 63.3, NEC4 ECC 63.5). They had created terminal float which is Contractor owned and they retain that in the assessment of compensation events. they are also entitled to claim "prelim" type costs for the 2.5 weeks as well, as otherwise they would have finished 2.5 weeks early and not incurred that prelim cost.
This is the same principle for option A or C in assessing the compensation event and the change to Prices.
If there was then a compensation event that then required an additional 2.5 weeks of work on the critical path, planned Completion would move by 2.5 weeks but so would Completion Date move by 2.5 weeks (see NEC3 ECC 63.3, NEC4 ECC 63.5). They had created terminal float which is Contractor owned and they retain that in the assessment of compensation events. they are also entitled to claim "prelim" type costs for the 2.5 weeks as well, as otherwise they would have finished 2.5 weeks early and not incurred that prelim cost.
This is the same principle for option A or C in assessing the compensation event and the change to Prices.