Not quite, Allan.
Selected and
Package.xml are two distinctly different subscription types. Updates to a package.xml file do not ever cause a change to the
Selected subscription. However, if you perform a module or project-level metadata retrieval when using
Selected, you'll see the package.xml file in the left-hand side pane of the resulting diff window. That package.xml does reflect your
Selected metadata subscription, albeit with absolutely no wildcarding...everything is spelled out explicitly. If you wanted to copy/merge that package.xml back into your local source directory, that would be a way of generating a package.xml from your
Selected subscription.
In practice, believe that folks who are automating deployment via Force.com Migration Tool or Salesforce DX CLI are expressing their metadata subscription as a package.xml file that's very carefully hand-crafted, and those who aren't should be able to use
Selected as a convenience for configuring the subscription.
Clear as mud? Seriously, though, let me know if I need to provide more explanation on this. I'm happy to do so.
Regards,
Scott