How does bemfola work?

[BlackLotus]

Starting bemfola on Tuesday which will be cycle day 6.
Been reading some similar comments on here and I'm confused now. Comments are suggesting its taken day 2-3 of cycle.
Now I'm wondering if I'm been told wrong?
How exactly does bemfola work?
For example in a natural cycle one follicle Is chosen by day 5.
I took clomid prior and was always told take day 2 to stimulate follicles.
Why are ivf drugs different?
Don't they need to be taken before a 'dominant follicle' is chosen? Would this not cause me to fail to stimulate new follicles

Im starting day 7. My clinic confirmed to stick to my schedule . No real explanation as to why but surely they know what they are doing ? I bloody well hope so.
My consent video also indicated day 2. Unless it's because they are batching collections so timing is same as other patients. Fingers crossed the meds do what they are supposed to regardless of start date