No, actually I was thinking of a different matter. While it may be, as you say, that a prospective member need only agree to the contents of a single statement of belief, the LCMS itself insists that Christians generally and Lutherans in particular have an obligation to agree on every last point of doctrine, large or small, essential or...??
If that is true for discussion purposes we would need a link in other to discuss the actual specific points in the matter.
I was able to find this>5.0 MEMBERSHIP
Synod congregations often distinguish between three types of congregational membership12: baptized, communicant, and voting 13. Voting membership may be open to all communicant members but may also be limited to males only14. Care should be taken that the age at which individuals may hold voting membership conforms to any requirements of state law. Many congregations restrict voting membership to persons who have reached the age of legal majority. This is especially important when decisions involving contracts and other legal matters are made. Again, membership in organizations whose principles and conduct conflict with the Word of God shall be prohibited (Bylaw 3.9.6.3.1 [a])15. Also, congregations are not to deny membership or other congregational privileges to any Christian because of race or ethnic origin (Bylaw 2.3.1 [a])16.
Example:
“This congregation distinguishes between three types of congregational membership.
5.1 The membership of this congregation includes the following:
5.1.1 Baptized members are all who have been baptized in the name of the Triune God and who are under the spiritual care of the pastor of this congregation, including the children who have not yet been confirmed into communicant membership.
5.1.2 Communicant members are those baptized members who have been instructed and are familiar with the contents of Luther’s Small Catechism, have been confirmed in the Lutheran faith, and accept the confessional standard of Section _______ of this Constitution.
5.1.3. Voting members are communicant members who have reached the age of ______ years.
5.2 The members of this congregation are received in the following manner:
From this link>LCMS Guidelines for the Constitution and Bylaws of Lutheran ...