Yeah on the mac it works fine. The keyboard just shipped with the Left Alt and Left Windows key in the correct positions, but they are mapped opposite in the firmware. Imagine how maddening it was in the beginning.
GP’s point is that many keyboards these days come with a Mac/Windows switch, and one of the things that switch does is swap the keycodes sent by the Alt and Win keys—the “Mac” behaviour is exactly what you’re describing. (The other thing it does is toggle FnLock for the F-keys.) So if I had a problem like yours with my keyboard I’d think that the Mac/Win switch were in the wrong position. If I’m reading page 9 of the manual[1] right, on the K4 the switch in question is right next to the USB-C port.
If you're not aware, you can remap modifier keys in System Settings on macOS. It doesn't have individual settings for left/right versions of a modifier key, so keep it in whichever mode has the modifiers on left/right paired with each other correctly, and then swap their functions to the right ones.
[1] https://www.keychron.com/pages/k4-keyboard-user-manual