Regarding delayed retirement credits; you indicated the SSA does not update they payments for up to 24 months regarding delayed retirement credits. If you make an initial application including the delayed retirement credits, what amount does the SSA pay for retirement until the DRC is updated and paid? Is it the PIA, or primary insurance amount which is payable until the the DRC is updated? As I understand it, you would only receive the PIA or full retirement age benefit until the DRC is calculated. After the DRC back payments, you would receive the increased amounts montly to reflect the DRC?
The answer to your question depends on when you file for benefits. For example, say you reach full retirement age (FRA) in June of this year, but you choose August as your month of entitlement. Although you would then earn 2 months of delayed retirement credits (DRC), you would initially only be paid your full retirement age rate (PIA). The higher rate including 2 DRCs would be due starting for the month of January 2019, but the automated process to recalculate your rate may not be done by Social Security until sometime in the year 2020. In the meantime, they would continue to pay you your PIA in this example.
However, say in the example above that the same person filed for benefits a year later. In that case, his initial rate would include the 7 DRCs he had earned through December 2018, and that rate would continue to be paid until Social Security's recomputes his rate to credit him for his additional DRCs for 2019.