Unwinding and NPV with or wo credit risk?

Hello,

to the issue of unwinding, NPV, NBV, gross carrying value and allowance under IFRS 9:
IAS 39 defines EIR (except of POCI assets) to calculate over the expected cash flows without including credit risk. (output is NPV, but without incorporated possible future defaults or pastdue payments).
Credit risk is incorporated in ECL (EAD*LGD*PD*CCF),… – if an entity uses IRB approach for allowances.
If we sum the two following parameters:
EIR*NPV(wo credit risk) and ECL (=credit risk in term of dollars), we get the total impairment for the period.
This means: unwind + loss allowances = total impairment.
And total impairment = Gross carrying amount minus NPV.

Why is NPV without credit risk?
Why unwinding is a part of impairment, when it doesn’t cover any credit risk?
What about POCI assets? Is there any unwinding, even if NPV includes credit risk?

Please, who can clarify me, Why all of three parameters (unwinding, allowance and impairment) can be calculated alone, and maybe using different methods (IRB, discounted CFs,..), because there needn’t to be always an equality: unwind + loss allowances = total impairment.
One parameter should be the result of this equation rather than calculate each of the three. Or am I totally wrong?

thank you for clarification.