I believe the default setting for profiles is to "close launcher when game starts". I have also tried setting that option explicitly by putting a checkmark next to the "Launcher Visibility:" option and selecting "Close launcher when game starts" from the dropdown list, to no avail.
I click the big "Play" button and Minecraft opens and takes the foreground. Everything is fine except for the fact that the launcher is still there, including window and dock icon. My active profile, however, says "close launcher when game starts".
What I expected to happen:
The moment that Minecraft starts, the launcher window disappears and the dock icon (grass block) disappears.
It is confusing that this doesn't work because when I use the application switcher to go between playing Minecraft and doing something else, I tend to switch to the launcher because it has the same icon that Minecraft used to have (which should be changed back IMO!).