If I'm not mistaken TW recently described this process as :- accounting for all the elements, starting with cost of block of aluminium, time, design, power consumption of milling etc to make the true cost of for example a suspension item, making it important at some point in commitment to produce this item.
Then I thought it passes to store inventory with that true cost attached to it, only when it's fitted for use will it come off store inventory and onto cost of racing. Unused items, I think, are like any other logical inventory system, place it back into store, without use, and it still doesn't count.
Keeping track of this process is quite some task to make certain that mistakes are not made. Auditing of records being part of FIA examination to verify compliance. These records need to be traceable, credible and accurate as any accounting system demands.
Emphasis is that I understand this from those conversations published with team principal etc, and so may be incomplete. But that is standard accounting practice methodology in stock flow. Depending on what adherence the cost cap rules are detailed to establish this process.
There's no benefit here in not using the parts though, as it's the design effect that needs to be assessed to confirm the pathway chosen, this will lead on to further establish if they are moving in desired direction. There's no point in making a second iteration as they don't know yet if it succeeds on track vs simulation.
It's not as if they were going to be super competitive at Monaco anyway with the original concept etc