I'm well aware of this, and I kinda assumed everyone was. GS markets itself to beginners and professionals. Professionals will buy a Mac without blinking if they need it to test their game properly. I know I will -- there's been enough demand for KarBOOM from Mac users to justify the expense.

Also, indies often get friends or random people on the internet to help test their games, so even a beginner who refuses to buy a Mac would have no trouble getting their game tested if the Mac compiler ran on Windows.

I had assumed that a Mac would be necessary for compilation. If that is the case, I think very few people are without access to a Mac (a friend or family member, for example). If it's not the case then even better!