Unless you've changed the drop table there, High scrolls don't drop there.
If I were to hazard a guess, I'm going to assume we're going to phase Redosmium out and start new characters on Sigmetal soon anyway.
As far as they need for option scrolls goes, I don't feel they're necessary anyway. The only real use for Sig, at this point, is to be used in professional craft to make the Extreme Mythril. Those recipes require empty slots to begin with, only a certain number of slots. Upgrade-type cores and slot extenders (questionably) are the only absolutely necessary upgrade items for Sig at this point.
If you're going to upgrade off of your starter Red Osmium, you're better off skipping to Mythril or Archidrium.