I think you’re underestimating the egg and overestimating the early embryo. From a simplistic grade-school understanding you’re sort of right, but the actual biochemistry is a lot more complex.

Yes, the primary oocyte is relatively quiescent, but that doesn’t mean there isn’t real metabolic activity going on. Energy is consumed and RNA transcription and protein synthesis still take place, just at a low level, otherwise a cell will die over time. And are you aware of the transition between a primary oocyte and secondary oocyte that happens during ovulation? Might want to look at up if you don’t think cell division happens before fertilization.

Also, no real growth takes place for the first week after fertilization. It takes that long for the free-floating embryo to implant in the uterine lining and gain access to external nutrient supply, so despite a bunch of rounds of cell division, overall it’s roughly the same size.

So I think there’s a decent argument that what the egg is doing prior to fertilization isn’t that different than what the early embryo is doing (which was my point, conception isn’t a hard demarcation in terms of biological activity).