Language locales not available in the panel front-end

I’m developing a panel view plugin that needs access to the defined languages’ locale. You can find all languages in this object:

console.log(panel.app.$store.state.languages.all)

Objects inside look like:

code: "en"
default: true
direction: "ltr"
name: "English"
rules: Array(0)

However, the locale setting is missing. Here’s what the PHP file for that language looks like:

return array (
  'code' => 'en',
  'default' => true,
  'direction' => 'ltr',
  'locale' => 'en_US',
  'name' => 'English',
  'url' => '/',
  'translations' => include option('oblik.easyvars.loader')
);

How do I get each language’s locale? If it’s a bug, I’ll file an issue on GitHub.