It may also be that the process of certifying some systems for use in a naval vessel is so long and arduous that it had to start long before the frigates ever saw water. Or a shipyard. By the time the thing actually launched, nobody wanted to go back and start from scratch.
We had a similar situation at a place I once worked where we had all these floppies and drives because that was the certified drive for a nuclear reactor safety shutdown system. Only once the SDSs were all upgraded were we able to scrap them.
