You can do the same thing with a small stop (or pinhole) and a neutral density filter. It is a "failure" in the sense that the regular time/intensity rule for equivalent exposure fails to provide equivalent exposure. It also causes a contrast increase because the effect (or failure) is more pronounced in darker areas making them proportionately even darker. And if you reduce development to compensate for the increase in contrast you lose yet more film speed (decreasing development does cause a noticeable loss of speed, it's just that increasing it doesn't actually increase speed, at least not very much.)

Glad it works for you but I confine my Fomapan exposures to 1/2 second and shorter. Anything longer gets TMY-2.