The scratch descriptor is being confused with the scratch pseudo-image used by Docker and others to indicate an empty image. Examples of this confusion include:

• The WASM Artifacts implementation: https://docs.google.com/document/d/11shgC3l6gplBjWF1VJCWvN_9do51otscAm0hBDGSSAc/edit
• Confusion from other spec maintainers: integration: Add TestImageInspectEmptyTagsAndDigests moby/moby#45592 (comment)

At the risk of creating another "artifact manifest" chaos, I think we should consider renaming the "scratch descriptor" and the associated media type to something that won't be confused with "FROM scratch" before we GA this and are stuck with the confusion. Instead of scratch, perhaps nil, empty, or blank?