made pm public
FP-100C packfilm was primary for passport photos. It can also be used for scientific and medical research, but for that use low ISO was limiting for certain situations. Many places uses various Olympus scientific devices that can use a instant back. FP-3000B as the high ISO film was very important.
Originally the plan was to use the Fotorama instant system and they did develop a MS-40 instant back for use with FI-160 4x5 Fotorama color integral instant film. I think they were going to develop a high speed b&w 4x5 integral version of that film, but the FP-3000B packfilm was just so much faster to develop after the capture compared to integral. FP-3000B was originally a minute, but later revision became 30 secs and 15 sec. iirc Polaroids 3000ISO Type 107 packfilm was originally 90 sec. My guess is that this reduced the need for high speed black and white integral, plus at the time they were unable to sell the film outside Japan because of the Polaroid lawsuit against Kodak since Fotorama is primary based on Kodak instant. Also Kodak never released a black and white for their instant system either, because of that there is also no black and white for instax to this day. Instead of a black and white 4x5 FI-3200B integral, they did develop a slightly faster 500ISO 4x5 black and white as the FP-500b45 peel and a regular size black and white 400ISO FP-400B. But that just my theory i cannot prove, based on reading their product development history and partnerships.