Thanks @d8vjork for the feedback!
app('auth') should be actually resolved by the phpstorm meta file if present (the Language Server supports this)
The LSP extension implements its own extensions internally - for phpstorm meta file, Laravel, PHPUnit, ... etc. And those extensions get activated when appropriate. So in a certain way, it is adapted to any framework we want. This allows us to extend and fine-tune the underlying type analysis and code completion.