For example, the SE electric boiler is an assembling machine with symmetrical fluidboxes, identical to the vanilla boiler. The vanilla boiler can be flipped, but the electric boiler cannot.
Copy pasting the discord discussion about this for reference:
Bilka — 12/30/2022 10:33 AM
@Wiwiweb just in case you didnt see, I was wrong, flipping depends on the fluidbox layout. I am unfortunately too brainfried to read the code what the layout needs to be right now, but you could make a doc request and get the info at some unspecified time in the (not near) future
justarandomgeek — 12/30/2022 10:35 AM
where is it, i'll see if i can make sense of it
Bilka — 12/30/2022 10:35 AM
FluidBoxPrototype::setupFlipping
justarandomgeek — 12/30/2022 10:52 AM
well i too am struggling to read this (mostly because i'm not familiar enough with how fluid boxes are structured...), but i did find the big comment with the extra clue that only some classes (which appears to be mostly crafting machines and pumps) have the extra rule that fluid indexes must match
