I thought the same thing as you when I read the bill for the first time. Indeed, I had understood that the special advocate was not bound by solicitor-client privilege in the context of his or her conversations with the individual. I see that you have taken note of this as well and are suggesting that solicitor-client privilege apply.
Generally speaking, solicitor-client privilege applies in all civilized legal systems so as to ensure that the individual who consults a lawyer is able to place his or her trust fully in that lawyer with the knowledge that the latter will not reveal what the client tells him. The lawyer is bound by solicitor-client privilege.
However, you are proposing that subsection 4 of Clause 85.4 provide that the judge be authorized to order that a member of the Review Committee attend this meeting between the special advocate and the individual. In such a situation, how could the individual have as much trust with regard to the conversations he is to have with this special advocate if he sees the latter accompanied by a member of the security service?