What puzzles me slightly is the timeline. Apparently the design(of the frigate) was requested in 1989; at which time the 8in disks were already on the way out. Shugart and Wang were already saying nasty things about the viability of the 8in back in 1976; and 5.25 were common, albeit as several squabbling standards, by the early 80s.
I’d assume that the 8-ins got dragged in thanks to the inclusion of some existing subsystem that was designed a fair while before the boat it was installed on; but between stuff lost in translation and the Germans perhaps being a trifle cagey about the details of their military ship systems I don’t have a specific candidate subsystem in mind.
Were 8in disks ever the more conservative and reliable option, with those crazy kids and their cut-price microcomputers cutting corners that Serious Customers simply wouldn’t? I never really used them, aside from some retrocomputing curiosity; but I never heard anything, in relation to the 5.25 or 3.5in, about how they don’t make them like they used to. I can only imagine that some salt air and the brisk vibration of a naval environment wouldn’t help them any.