@Hawkido by your logic, Allomancy does not require metals, only that the user's power is Preserved.
This is faulty logic, as the Shard's Intent relates to how power is gained.
It only means that in alternate universe, where Ruin ended somewhere else, his magic would still require loss of power and Preservation's magic would still be end-positive. That quality is unrelated to what the magic actually does.
On Roshar you still need metals to access Allomancy - not some kind of spren, or bond, or Oath (or whatever Roshar's focus is) - then why should Hemalurgy unexpectedly use another focus?