Except that the standards aren’t quite equal. The Pope can, with some degree of reason, claim to be speaking that which all good Catholics must believe, in that by the laws of Catholicism, they have consented to his adopting that role, and if they remain good Catholics, they will agree to what it is that he teaches. Similar statements with appropriate variations and a bit less force can be asserted of a Methodist General Conference, a Presbyterian General Assembly, Gordon Hinckley for the Mormons (I forget his exact title, but he’s considered to have a prophetic voice for our days by good LDS), and so on.
Note that the Baptist Faith and Message places the onus for belief squarely on the individual believer, and the congregational polity places the formulation of doctrine in the hands of the local church. The SBC and its parallels are not denominations in any real sense; they’re like a Council of Churches for Baptist churches.
Or that was the theory before about 1985. Under Paige Patterson and his successors, the SBC abnegated its role as a common voice and conduit for missions money for its members, and amended the BF&M to teach a strict fundamentalism. As Sauron and others have noted, the resulting exodus of moderate people and local churches from the SBC was partially by compulsion and partly by “voting with their feet.” (I’d note the church a few miles west of Charlotte NC which was expelled from the state Baptist Convention (and presumably from the SBC in consequence) for baptizing two gay men, a couple, who attended there and presented themselves for baptism.)
So it is to some extent correct but to a greater extent incorrect to presume that the SBC leadership speaks for its 16,500,000 alleged members; it speaks for itself, and presumes to speak for them, but without any authority or consent to do so. Sauron or other Southern Baptists, please correct this if there is any error in it.