Can it optionally apply formatting?

[jssuttles]

The DICOM JSON schema does not have _rawValue, so other things that might be able to read the previous format can't read the new format.
https://dicom.nema.org/medical/dicom/current/output/chtml/part18/sect_f.2.html

[pieper]

Any of the elements with the _ prefix would need to be stripped if you want to treat dcmjs datasets as native DICOM JSON. The _ elements are used for internal processing and to support lossless round trips.