Suppose having a package that doesn't use all the columns defined in its Data Flow source component. It seems impossible to get warnings such as:
"The output column "A" (aa) on output "XXX" (xx) and component "YYY" (yy) is not subsequently used in the Data Flow task. Removing this unused output column can increase Data Flow task performance."
using the command:
DTExec /File "<full_path_package_name>" /Validate /Reporting EW
I suppose DTExec validation doesn't throw out SSIS.Pipeline validation phase warnings.