Firstly, I have no idea what you mean by “the nutshell answer” !
Assuming this is for original work, as the Contractor owns both the TRA and terminal float, in terms of calculating delays due to compensation events, it does not matter where the TRA is put, although in terms of understanding the programme, transparency etc. it does !
If the Contractor does not use up the TRA in a critical activity, it will be reflected in greater terminal float in the next programme submission. Likewise the opposite if more time is needed than is allowed as TRA.
So if a compensation event occurs and puts back Completion by say a week, then according to the contract rules, the contractual Completion Date will be put back a week, regardless of whether the Contractor is ahead or behind on its original programme. And the Employer/Client would pay for this week delay only. So I do not see how the Employer is paying twice.