Was on the Fujica 645... GS645 folder, GS645S, and GS645W (last one zone focus)
These camera's all had T... they did not have B. Using T on these camera's was cumbersome because putting the camera on T, would open the aperture when the shutter was pushed. However, to close the aperture you had to change the shutter speed ring on the front of the lens. The shutter button did NOT close the shutter.
The simplest way to do this without blurring the photo, if that last second would be noted by the film, was to put a hand over the lens and change the ring to close the aperture...
YEP! that's it.
Now, I have never seen the big Fuji's or Fujica's with a T setting, since this seems to be Fujis solution for T. All my lenses for the interchangeable lens Texas Leica models had B.. No T.
I do not have firsthand experience on the I and II GW/GSW models, but I did have a GSW III and it had B... No T.
I think after the frustration of the T on the 645's, Fujica/Fuji gave up on T. I suspect also, since one does not generally find T on medium format camera's Fuji finally recognized that T was more appropriate for Large Format, where a camera could sit on a tripod for a long exposure. Fuji probably figured out the big rangefinders were, more often, going to be handheld, and T would be wasted on the camera, as just more parts to fail....Unnecessarily.
Bottom line... a second push of the shutter button never completed the T cycle. You had to change shutter speed to do so. Also remember that Fuji was probably producing more large format lenses during that era, and somehow confused the need for a T function into the Medium Format media.
Prove Me Wrong, Or in Cybertalk PMW?
Last odd point... The big interchangeable Fuji rangefinders did not dry fire without film in them, unless you changed the film type selector from Roll to Sheet film. Then you could dry fire on Sheet without the sheet film back on the camera.
The interchangeable 670 and 690 cameras had an option to shoot sheet film by a sheet back and the selector on sheet. That is the only way the camera will dry fire, until you put a roll in and select R.
The GW/GSW models had no option for sheet film and thus may have dry fired without film.