Earlier quoted context omitted.
Yep, fair enough, if it's a strict definition. You could potentially then have weird edge cases in the other direction, though; if the same sex chromosome layout in related species X and Y leads to different sexes due to the size of the gametes (especially if the size of the gametes was pretty similar to start with), that seems very odd/confusing.
It looks like there are cases where the size of the gametes are identical. But when this happens they don’t refer the organism’s sex as “male/female” and instead use “+/-“. https://en.m.wikipedia.org/wiki/Isogamy Going a step further I found this: >Depending on the group, different mating types are often referred to by numbers, letters, or simply "+" and "−" instead of "male" and "female", which refer to "sexes" or d…
All individuals of this snake are female (presumably 'female' here is defined relative to other snakes) and reproduce parthenogenetically (sic?). By your definition, these wouldn't have a sex at all, presumably.