Every microgreens farmer who grows sunflower shoots for their customers knows that the seeds on the market are inconsistent.
Even from the same supplier, each seed lot performs differently so you never really know if you're going to get a good batch that actually germinates and gives a decent yield.
The seeds are hit-or-miss, even from your favorite seed suppliers, and sometimes they are even out of stock. Why even bother growing sunflowers in the first place if they are going to be so much trouble!