[gregdoesit]

I was on the team who built this, five years ago. I left Microsoft about that time ago. I don't have information on how and why decisions are being made now.

Having worked at Microsoft though, if your team cannot guarantee that a feature works on a browser that uses some non-standard things, is a decision that product will make on how to proceed. Display a warning or just don't support? Perhaps there might be security issues in the future the company wants to avoid this way, knowing they could not patch it? And so on.

Beyond speculation, I don't have much more to offer.