Phase One, did not use the cropped 100MP sensor, they went for the non BSI 100MP full size 645 chip (I realize that is a relative term). The IQ4 100MP uses the Trichormatic chip that came out in late 2017, for a variant of the 3100.
P1 IQ250/150/350 all use the same chip 50MP chip, P1 IQ3100 and 3100 Trichromatic use the 100MP non BSI 645 CMOS, Trichromatic uses a unique version of the same chip in the 3100. P1 IQ4 100 uses the same Trichomatic chip 100MP non BSI, IQ4 150 has the only BSI chip I know in a MF back or camera sold and available on the market.
Fuji should be the first company to bring a cropped BSI 100MP chip to market in their follow on to the 50S/R camera.
Paul C