I don't understand your comment. I was responding to the parent stating: "Apple's been taking a number of steps over the last few months to show that they take Safari/WebKit development seriously." I'm annoyed because there are Safari-specific issues that as a Windows user I cannot debug, thus my comment that I cannot take Safari seriously. Like it or not, Windows is the dominant desktop platform.
I think what the parent is getting at, is that you've got the same problem regarding IE on Mac. There are IE specific issues that I as a OS X developer cannot debug.
At least Microsoft offers free VM images for precisely this purpose. Meanwhile, OS X barely works in a VM due to the lack of graphics acceleration (plus, running such a VM on a non-Mac is illegal).
Cross-platform means you have to test on multiple machines. A company that's taking web development seriously also needs Mac, iOS, and Android devices to test on. Or borrow them every now and then, or sometimes virtual machines will work.
(I do often skip testing on Windows and iOS for hobbyist stuff since I don't normally use them, but I don't blame other people for it.)