Yup, I doubt he has experience working in the games industry. Many engines support multiple graphics APIs and there's often only 1-2 employees implementing/maintaining them so speaking about vendor lock-in is not a strong argument.
How is that a counter argument to anything? The need to support multiple APIs is not free. It's a tax on everything else.
You're right that it's not free. But compared to the whole game engine codebase size the renderer backend is usually not big.
It is a waste of time that could be avoided. And exists only becasue of insistence on lock-in by the likes of Apple.
Lock-in proponents bring their kool aid. Not impressed. Gaming industry is pretty messed up when it comes to lock-in. Everyone is paying this tax.
I am aware of my limitations as human being in this society, speak from actual work experience, and will use any tooling that I rant about when it is on the best interests of the customers, regardless of my personal agenda.