I am asking to see if anyone has some clarity on whether this is a legitimate reading of the relationship of leaven and yeast:
Leaven is not yeast per se. Bread made today from packets of yeast is unleavened bread. Leaven means the lump of sourdough is broken off, mixed with flour, water, etc., and then the new loaf rises. Meanwhile, the remaining sourdough starter is fed with more flour and water, and left to rise, to be used the next day. This can continue for many years; but Israel was told to cut it off and start over every year (from James Jordan's commentary on Daniel, entitled The Handwriting on the Wall, pg. 72, footnote 24).