application/json Content-Type character set

According to the OWASP Application Security Verification Standard:

V11.3 Verify that every HTTP response contains a content type header specifying a safe character set (e.g., UTF-8).

According to the RFC for the application/json Media Type:

JSON text SHALL be encoded in Unicode. The default encoding is UTF-8.

Since the first two characters of a JSON text will always be ASCII characters [RFC0020], it is possible to determine whether an octet stream is UTF-8, UTF-16 (BE or LE), or UTF-32 (BE or LE) by looking at the pattern of nulls in the first four octets.

If you're encoding is in fact UTF-8, this implies there is no security benefit to setting the Content-Type header to application/json; charset=utf-8 instead of just application/json.

Is it reasonable to make an exception to the OWASP rule for application/json?