Doug, a servant of the Divine, to the churches and congregation wherever dispersed around the globe: How wonderful it is to hear from you so that I may be of service to you. May you encourage diversity now and always.
Allow me an opportunity to answer your question. A church does not need to wait until it has thirty members before it divides into two or more churches. Most churches have less than a dozen members as it simplifies church services.
Smaller groups are more able to focus on the needs of the individuals than larger groups. Smaller churches also have the advantage of being able to meet without costly overhead expenses. At the same time, they provide for more diversity by finding common interests among the members of the church.
The limit of thirty members per church is an upper limit on the human ability to intimately interact with everyone in the group while still being able to gather privately in a home. There is nothing magical about the number.
Groups that split are encouraged to continue to interact with other churches as we are all of the same faith. Social gatherings of multiple churches are not forbidden. However, the church, remaining small, provides for a more focused help to the other church members become better followers of the faith.
Go in peace. Encourage diversity by intimately helping one another become stronger in their faith now and forever. Amen.