can anyone explain why is this happening and if it is an expected behavior?
It is the expected behavior, the values set in the editor should overwrite all other values.
This way you will always have constant new game no matter what is changed. Think of the editor values as the default values.
You need a loader function that changes variables after startup, for your variables to change.
For example if one of the variables is "soundVolume" then it has a backup default value from the editor, but on startup it will load the value from the "playerPreferences" list.