Cannot follow some standard modules

It happens for Random module and for other more complex modules such as Flux.
It's recognised as a module, but still warns and doesn't find its symbols
Found that with Julia 1.6.1 only Flux is not found correctly. With Julia 1.3.1 I have the above errors
I'm getting something similar while using Spacemacs.
This is using Julia 1.6.1
I can observe this too, in both Spacemacs and VSCode running on NixOS.
I have tested both julia-lts-bin (1.6.6) and julia-bin (1.7.3).
Whenever the language server is started with a custom project path, only packages that are explicitly added to the project are indexed.
I get a “Missing Reference” for many standard modules, e.g., using Pkg or import LinearAlgebra etc.
You can (should) add standard modules to the project.
Ok thanks for the clarification :) I am doing so in most projects.
Actually, the above "issue" arose when I tried to test one of my own packages and tried to circumvent https://github.com/julia-vscode/julia-vscode/issues/1023 by starting a LanguageServer from a project containing only said package.
I was not sure if all the "Missing Reference" hints were intentional when I then used Test for example.
You can (should) add standard modules to the project.
what does that mean