There are only two parties that promote current gamete production as necessary for "the biological definition of sex": Prof. Griffiths and Steersman. There is only one party that says gamete production alone is not sufficient, and that would be Steersman.
Regarding Griffiths:
Using my next level web skills, I checked out Griffiths' wikipedia page. There I am told:
Griffiths, together with Russell Gray developed a theoretical perspective on biological development, heredity, and evolution known as developmental systems theory (DST).
Following that link, we get this:
https://en.wikipedia.org/wiki/Developmental_systems_theory
Developmental_systems_theory Developmental systems theory (DST) is an overarching theoretical perspective on biological development, heredity, and evolution.[1] It emphasizes the shared contributions of genes, environment, and epigenetic factors on developmental processes. DST, unlike conventional scientific theories, is not directly used to help make predictions for testing experimental results; instead, it is seen as a collection of philosophical, psychological, and scientific models of development and evolution. As a whole, these models argue the inadequacy of the modern evolutionary synthesis on the roles of genes and natural selection as the principal explanation of living structures. Developmental systems theory embraces a large range of positions that expand biological explanations of organismal development and hold modern evolutionary theory as a misconception of the nature of living processes.
Just to give an indication of where he is coming from. He's an ideas man. Griffiths' main point about defining sexes, in the Aeon essay, is that if we try to come up with a universal definition for the sexes based on anything else but gamete production, we run into "problems" with, eg, worms that produce one gamete, then the other, then both, or something like that. But I don't think any biologist working in a specific field has the "problem" of coming up with a universal definition. They need a definition that's functional for their work. I mean, it's a practical definition for a philosopher, because generating ideas that may or may not be relevant is part of the gig. As for his claim that his definition is the one that biologists use, there are no citations to be found.
One line from the Aeon essay, I found kind of funny, cause it seems like Griffiths himself doesn't consistently use his own definition:
Most groper are smaller, brown females. They are all born female and become sexually mature after a few years, when 20 or 30 cm in length.
I understand Griffiths, he's nitpicking on the basis of formal logic. But how is it relevant to anyone else? The Aeon essay uses social issues about trans people as a hook at the beginning, tells us what "the biological definition of sex" is in the middle part, and then bookends his narrative by bringing us back to trans issues, and his takeaway is that we should definitely
not use this definition when it comes to social policy.
I don't understand Steersman. He seems adamant that everyone adopt his unique definition of sex (which is even more strict than Griffiths') but then also disregard that definition when it comes to trans issues. Sorry, what is the point of this whole exercise?