Allowing the windows installer file to be elsewhere in the sources subdirectory
Actually the MSI is located in the root of the source file then SCCM will be able to detect it only at the root of the source file. But if the msi is Under another directory why not be able to set that localtion?
It is only when you use the wizard to import a MSI.
Manual creation or after the wizard is done, you can set the source path and command line independently.