My comments were based on the logic how most *A airlines operate in order to feed the Starnet database that keeps track of all the flights you took and reports them to the crediting FFP. Most airlines have a CRS to sell and administer tickets, including the coupons they get send from codeshares etc. When checkin opens, the information of the flight is tranferred to a DCS which may or may not reside within the greater system that also hosts the CRS. LH for example uses Amadeus (a customised version of the GUI called guideRes) for CRS and Amadeus Altea Inventory for RM, but a Unisys modification based on a 40 year old system for DCS (the GUI is called Pictures). LO & OS is similar, SN & LX use the EDS/HP axsRes and axsControl.

Some information is pushed back and forth between the CRS and the DCS and updated in a final version after the flight is closed and accounted for, but not all *A partners update all the fields, and FFP numbers are not on top of their priority lists. LH for example will pull the FQTS and FQTV information into Unisys one time only and changes there will not always come back to the CRS, unless the agent checks you out from the flight, updates the original PNR in the CRS and check you in again. Most agents will just change the number in the DCS and reprint you a BP that shows the new number, but not the one that will be reported back to the Starnet database. US is a prime example of this too.

So yes, I'm certain the examples you cite may work again, but not for all *A carriers and FFPs. *A is working on a solution and most carriers are migrating to the full Amadeus Altea suite to harmonise the system. UA has clearly opted out after the merger with CO since the Shares customisation CO had running gave them an instant upgrade, but the effort to migrate to that in 2012 and then to Altea in 2015 would have been too much.