Moby has some registration code to handle OCI manfiests here: https://github.com/moby/moby/blob/6f069f14e6a76f2a3cdf50a089e67429581d7cc8/distribution/oci.go#L15-L28

Notice that it is using schema2.DeserializedManifest.

This commit 1d47ef7 which performs validation of the media type field on unmarshal is breaking that logic.

We can come up with a means of updating Moby... however this code looks wrong to me.

1. Strictly as someone who doesn't spend much time on this codebase it seems like a bit of a smell to do data validation while converting formats (json bytes to go struct).
2. It also seems incorrect to assume that the value of the field is always a particular value this deep in the code.