If this seems strange, you probably do not use macOS or haven't used it for long?
It's not called macOS any more and hasn't been forever. I've been using a Mac daily for almost 10 years.
I'm not a big Windows guy. I dislike Windows and only use it when I'm forced to. So I'm not coming from the perspective of a long time Windows person who is trying to make everything seem like Windows. I've been using different computer OSes for more than 25 years.
However, I realize that I'm not a typical Mac user. I don't really buy into their whole ecosystem. Nor do I try every new UI feature that they come up with. I'm also not really into the concept of having a totally clean looking work space with only one app showing at a time. I'm perfectly comfortable with 5 or 6 apps open at once, with the one I'm using on top. I alt-tab between apps constantly. ...and alt-~ between windows in the same app (like web browser windows).
So the idea of minimizing or "full screening" apps is rather foreign to me. It never occurs to me to do that. So, despite having used a Mac for 10 years, I've never tried pressing the X on a media player expecting it to keep playing. So I just tried some experiments.
VLC and Itunes both react like you say: The window disappears but the app keeps working. Bringing the window back from the window menu lets you see where you were. With other apps like web browsers, text edit, Photoshop, etc it closes the window you were working in and it's *gone*. You can't bring it back without opening the document (or web sites) you were on before. Which is what you expect.
So this is just a media player thing. It's not a generalized OSX behavior. Your observation and request are no less valid. You just make it sound like every app works this way and they don't. Just media players. So maybe MC should do this too.
Is this your most important thing that you would like the MC team to work on for Mac? I feel like there are far more important things to bring to the Mac version other than "make it more like a native app". I could care less how the menus work, whether it goes "full screen" or if this minimize on X behavior works. But apparently there are people who think MC for Mac is "done" except for the Mac specific UI fixes. You're certainly not the first person to ask for this and other more Mac-like behaviors.
I just don't see why it would be important compared to something like making Video playback features work closer to the Windows version.
On the other hand, no one at JRiver cares what I think.
I'm sure they consider all of these requests and try to pick the ones that will satisfy the most people and draw the most people to buy or upgrade their MC licenses. Maybe making MC more "native Mac-like" would draw more new customers. I know it's look and feel put me off at first because it's so non-mac-like . It's been so long I had almost forgotten that my initial reaction to MC was negative.
Brian.