yes, good that you actually recall the link. I cannot find the conversation myself.
I have called local isc2 support today, and I have been provided with feedback that I can have "grace period" - 90 day (which is written on the CPE handbook), if it's under very tight situation (mean you concentration is very close to the cycle ends) , however, i have also response 90 day grace period is just "submission", the CPE you have earned still must before the "expiration".
I have a written response to isc2 asking a clarification on Amanda's 6 month period if there is any official documentation and also from a "fairness" perspective, it's not really fair if the cycle start before the concentration start and while the CPE requirement is still in "full". For example someone may have close to 3 year to complete the require CPE, while someone may have 6-9 months to complete the 20 CPE.
I will wait for the official response, once I have more light, I will post further update.
For the automatic CPE earn, I will have extra CPE anyway, so I won't delete and this also won't get audit anyway because it's automatically added CPE won't get audit according to the CPE handbook.
I highly suspect they didn't understand what you meant as this circumstance is not listed in the CPE handbook, and as you rightly say it's likely they're confusing it with the 90 days grace period you get to enter CPEs that were earned within the cycle.
Although it's not written anywhere, ISC2 are a reasonable bunch and I think it would be easy to argue, if needed, that you completed a pro-rated number of CPEs for your concentrations.
e.g. If you have 12 months to the end of your CISSP cycle at the point you earned a concentration you would only need to complete 20 / 36 * 12 = 7 CPEs.
Would be good to have a definitive answer though as this is something every new concentration holder has likely wondered about so I'm looking forward to your update!