Hi Josh,
Sorry it's taken a while to respond to this - I was busy with the Numbas v9 release.
No, deep linking doesn't solve the problem.
The root of the problem is that there isn't a standard way for the platform to tell us when a link is copied from somewhere else. So while the new LTI 1.3 deep linking scheme means that a copied link still sends us enough information to work out which resource to show, we don't know it's copied. You don't want last year's attempts mixed up with this year's, so the ideal behaviour would be for it to automatically make a copy of the resource, using the same exam but with a fresh empty list of attempts.