It would seem that if a developer OS was going to work correctly on any machine, ever, that would be the one, since an issue there would bug the largest possible group of people who were capable of doing something about it.
But it doesn’t. I think he has a valid point.
No, this is simply untrue. Once you step outside of the US SV and WebDev bubble, there are millions of developers writing code for on Windows and Linux for stuff that you never even heard of. Mostly because it's unsupported on Mac due to the locked down ecosystem. Obscure machine controllers and their drivers, planning software, banking software, regulatory mandated software for certifications, etc.
I did industrial cs, so development was mostly focused on embedded devices and nobody here used a mac for anything.
Wouldn't have worked anyway, since people tend to be tinkerers. That is usually not a group using locked down environments.
You're certainly correct that that's due to a combination of nobody caring enough to pay for that to happen (and the few people who could in fact do something about it simply configuring their own personal machine to work correctly.)