I google searched it, and this is what i found:
"By placing a saliva sample on the Ovusight lens, you will be able to clearly see the "ferning patterns" that occur when estrogen levels rise. This estrogen rise signals the onset of ovulation and this is your best time to make love so you can get pregnant." https://www.menstruation.com.au/fertility/ovulitefertilitymicroscope.html So I would say you're right!
Also, this website explains the difference between "natural progesterone" versus provera. Maybe this explains the ferning issue? https://allonhealth.com/natural-progesterone/provera-is-not-progesterone.htm