If Apple manages to lose both designers and developers, I think the whole ecosystem (not just macOS) will suffer more than Apple's management realizes. I also don't think it's possible to run the numbers on this scenario.
Without the insistence of so many designers on using a Mac, would macOS really have won a foothold in corporate environments? If enough designers and developers switch to Windows, who's to say that macOS won't slowly turn into a hobbyist OS that no IT department wants to support (like Linux, or Macs ~12 years ago)?
Apple doesn't care about the corporate market. They care about individual users. And as long as the CEO wants their shiny Mac (also, see iPhone, iPad) then the IT dept will support it. Your argument might have been valid a decade or so ago, but since then, every home has a laptop or three, and BYOD happened.
In my limited experience, management often uses a shiny iPhone, a shiny iPad, but then a Windows laptop (or none at all). I can't find any statistics to back it up, though.
Without the insistence of so many designers on using a Mac, would macOS really have won a foothold in corporate environments? If enough designers and developers switch to Windows, who's to say that macOS won't slowly turn into a hobbyist OS that no IT department wants to support (like Linux, or Macs ~12 years ago)?