You don't have your project in the KADOKAWA/RPGMV folder, do you?
Of course not
:)
path "KADOKAWA/RPGMV" refers to path end in %local data% (on Windows).
Those are actually locations where local user data for any installed application are stored.
After deployment we get standalone game which isn't installed and doesn't need to be installed in order to work.
That's cool for Linux or Windows but can create problem with Mac since Mac (in most cases) won't allow applications to write data in locations that are not allowed (like putting saves in Save folder in your game folder after deployment). And that's why this plugin comes very handy, since it writes data in an allowed and logical place.
When you deploy your game RPGMaker makes a shell for each platform (I'm referring to Mac, Win and Linux deployment) and adds your game specific data. So that works ok by default. But it also copies information about where RPGmaker stored data is set for a user that deployed the game.
This could be a problem for example if some user plays two games that are using the plugin, but file package.json wasn't changed manually. It would store data for each game in the same place.
Note that deployed game is never actually installed on your computer! It's a standalone application. So this local user data can't be generated based on install data, which is the case when you install RPGmaker (or any other installed application).
My suggestion for improving RPGmaker would be to add an option while deploying to make an installation deployment file package (like you usually get when you are installing most games). This shouldn't be a problem to make and we all could this way get more "professional" looking product. Also adding option for user to choose where will those data be stored (in local data or game folder) would be nice, but again – would that option be a problem for Mac users? Probably...
To make myself clearer - if you ever tried to make Android build what you need to get is an installation apk game file of your project which user needs to install. That's something that would be useful for other platforms.