As the answers to the linked question stated, Blender comes with its own Python version. This is correct for Blender 2.7x and 2.8x.
You can have more than one Python version installed on your computer anyway, but the specific reason for why this works in Blender is a quite old concept, that dates back to the time, when shared libraries were invented.
If you start any software that uses shared libraries (or any other form of additions), it first starts to look for them in its own installation directory. If it doesn't find there, what it's looking for, it tries the directories that are stored in the user variables and then the system variables. If it still doesn't find what it's looking for, it throws an exception error.1)
In short - ideally you don't have to do anything, since Blender has its own Python version and 3.7.X makes entries to the system variables during install. However, if you want to use even more Python versions, you either need to add another system variable for each version or make use of pyenv.
1) A variant to this behavior called DLL Injection enables good things like ENB or ReShade, but also bad things like viruses.