I didn't know that was intentional. And I've seen the iron bucket eating in non-FTB packs too (ATLauncher, Technic Launcher etc.) but with different things.
I also noticed whenever I want to make seeds of the metals (Tin, Iron, Copper etc.) with the Runic Altar, it doesn't work.
I put all the needed ingredients on it, drop a Livingrock on it and right-click with my Wand of the Forest (in Bind Mode) and it seems to work but doesnt give me any seeds and resets the accumulated Mana back.
(And yes, I did this when the Altar was shooting lightning out of it indicating that it's ready.)