i gave it a little thought and maybe beds and cages are not considred machines at all, you unly get the hunger rate decrease in bed because of the "resting/ko state", not the "current work". i think people in cages get the "idle" state but i didn't pay that much attention

Oh I see. I was trying to experiment with those settings "hunger rate" with beds and cages, but it seems that it is not taken into account for functionality with function BF_CAGE and BF_BED :/

usually any "machine" as far as i know. whenever the game tell you "operating machine" it's referring to that type of building, meaning the character is doing a task and that task can be altered. for what i observed all machines have the same parameter, which will show in game in the "current work" entry when you hover over the character's hunger bar. changing this parameter alters hunger rate. almost all machine have that parameter set to zero, exceptions are stone, iron and copper mines, which i believe give 1.2 times hunger, beds that give .5 and stools and pillows which range from .75 to .66. i could have taken any machine and altered it this way, the only reason i didn't is i didn't want people to have to actually consume and produce anything to get the malus, it's meant for testing so it's supposed to be as easy as possible to setup and require no micromanagement at all

Haha, nice. Kinda inspiring to think what would be possible in the department "what other buildings would manipulate hunger and in what way".