Is the past removal of Load/save ,pln files after FLY still technically valid

When MSFS was launched, it was an option to ESC from FLY, and then Load or save both FLT & PLN files.

More recently the option to load or save the pln file was removed, the reason not being technically very clear.

So now, and changes to the ,pln done once in the plane, cannot be saved through the MSFS menu system although the PMS50 GTN750 still successfully CAN save the pln to the Datastore, and at any time after retrieve it,.

(but strangely one can save the more complex FLT file, that contains the flight plan.)

SO

(1) What was the technical reason for the change to prevent the .pln from being save once FLY had been evoked. ?

(2) Is that reason is not now strictly valid now, can the saving of .pln file be restored at the same time that ,FLT files can be loaded or saved. ?