MC18 for Mac was first available in February of this year. That's 7 months ago. It was introduced in the middle of our MC18 cycle. MC19 has been available now for a couple of months on Windows. We're doing our best to get them in sync. When they weren't, we couldn't offer MC19's features on the Mac, and Library Server was on a different version, so that playing media from a Windows server to a Mac wouldn't work. And so on.
I'm sorry if you feel like you didn't get a good deal. It's not our intention to make anyone unhappy, but sometimes it's beyond our control.