draft-ietf-smime-idea-04.txt: parameters question

The IDEA in CMS draft specifies the parameters as follows:

  IDEA-CBCPar ::= SEQUENCE {
    IV  OCTET STRING OPTIONAL -- exactly 8 octets }

Is there a good reason for the SEQUENCE wrapping? We already 
have a CBCParameter structure defined in RFC 2630, and it
seems a shame to be inventing a slightly-differently-shaped
wheel.

Cheers,

William