I perfectly understand the licensing model of the App Store and its implications. I apologizes if I sounded rude; didn't mean to offend anyone.
About the buttons: I could argue that yes, they advertise a single platform purchase, but I was so naive I thought I could download the Mac version through your portal anyway once my purchase was verified. Of course, it's my fault being an expectation I only built by myself according to the policy of other players in the market, and I take full responsibility for it.
Anyway, I understand that this is your business model, and I respect it. Unfortunately, it doesn't fit my needs.