-e: see title and thus visual studio won't know that the dll is no longer part of the project

-repro:
--have Visual Studio installed and your default C# editor for Unity (probably works with other editors too)
--open attached project
--double click the TestStuff.cs file to open it in VS
--wait for it to finish
--open package manager
--Disable the Physics module
--notice that you now get errors in Unity saying that the script is referencing things that are not there
--NOTICE that you don't see any errors in VS about this
--close VS
--double click TestStuff.cs again to open VS
--notice that you now see errors about BoxCollider