The answer to your question is No.  There is no contradiction between FAR subpart 17.2 and FAR 17.205(a).  FAR subpart 17.2 does not apply to construction contracts which means FAR 17.205 does not apply.  There is no further guidance in the DFARS and DFARS PGI.  However, the FAR does not preclude you from documenting option decisions and including them in your contract file which is also good business judgment.  Please verify this with your agency regulations.