See this doc.

At the time of writing, a tenant is initialized with dozens of splits which are mostly useless since the adjacent ranges are mostly inactive/empty and share a zone config.

If the number of replicas per node ever becomes an issue (i.e. if thousands of tenants share a small cluster) we should consider omitting these unused splits. Instead, a split should only happen by load, size, or zone config (the latter of which the tenant is unlikely to ever be handed free reigns over).