The reason is that if there is some legitimate reason to add a name to the speakers list, I'm sure committee members will not object to adding that name. If we find there is some additional need to add a new witness, then we'll add a new witness. We'll just do it unanimously. But what we don't want is for one or two committee members to have the power to extend the witness list infinitely, into perpetuity. The only reason anyone could possibly want to empower a single member of the committee to add infinite numbers of witnesses is if they were intending to delay the work of the committee.
So why not just agree that unanimously we can all, on a reasonable basis, extend the witness list where necessary?
Thank you.