proposal: omit the last bullet from this section:

2.24.0.17.2 JSON Signature rules 

When the signature is an JSON Digital Signature (contentType = application/jose), the following rules apply:

• The Signature.data is base64 encoded JWS-Signature RFC 7515: JSON Web Signature (JWS) 
• The signature is a Detached   Signature (where the content that is signed is separate from the signature itself)
• When FHIR Resources are signed, the signature is across the Canonical JSON form of the resource(s)
• The Signature SHOULD use the hashing algorithm SHA256. Signature validation policy will apply to the signature and determine acceptability
• The Signature SHALL include a "CommitmentTypeIndication" element for the Purpose(s) of Signature. The Purpose can be the action being attested to, or the role associated with the signature. The value shall come from ASTM E1762-95(2013). The Signature.type shall contain the same values as the CommitmentTypeIndication element.

Rationale:  There is no  "CommitmentTypeIndication" element in JWS. Nor as far as I can tell a corresponding element.  you could add a private header parameter name.