Although I understand why this would be a feature, it messes with the launcher and reduces possibilities

Let's get the story straight. I launch Minecraft Java 1.20.2 (Although it'd probably also has to do with other versions) from the latest Minecraft Launcher. Once fully launched, I once again try to open the Minecraft Launcher, but it'll switch to the just opened Minecraft Java 1.20.2 window. 

Before I get to the consequences, I'd like to list a few other issues that occur because of this feature:

1.  After clicking "Play" on any selected version of Minecraft and waiting for the launcher to close, there is (depending on your computer's power) a few second window before the game itself opens up. Opening the launcher again within this few second window will result in and error, shown in the first listed image.
2. After clicking "Quit Game" within Minecraft Java and then immediately opening the launcher, the same error message will appear as listed at issue 1
3. Trying to open the launcher after starting up your computer may sometimes result in it thinking your game is open, and therefore not opening the launcher itself. This requires a full computer reset before you can start up Minecraft

Consequences of this feature:

1. If you have a second account, which you'd like to open in a second game window, this will be impossible. People usually use this feature to record something from a different perspective, or test something as if you'd be playing with your friends.
2. Changing your in game skin has to be done in minecraft.net if your game is open. Usually you'd be able to quickly change your skin in the launcher and log out and log in to the server you were on, and your skin will change. This now requires full game reset

I understand this feature is implemented so that the issue of accidentally having two games open (which could interfere with the game files) is not possible anymore. But it gives a ton more consequences that would be considered far worse. 

I have no idea since when this issue has been existing, but I've only started noticing it a week or two ago.