The profile page for the "New" US Core DiagnosticReport states:

When US Core is balloted for R4 it may be merged into the existing profile.

It is built independent of the US Core DiagnosticReport lab profile for initial testing. When US Core is balloted for R4 it may be merged into the existing profile.

US Core is now being balloted for R4 and it is unclear if the ballot is to merge it with the existing profile or not. Given that the two use cases can be distinguished by category value, and assuming that the two profiles are compatible (with minor tweaks like changing the category from fixed value to VS), I think it makes sense to merge these.

If these are not merged, however, please make the "new" profile's name, id, and URL more descriptive. StructureDefinition-new-us-core-documentreference is not descriptive – and what is "new" now, won't be new in a few years.