Before revision:  The improvement of runtimes with the Recursive-DBSCAN method is because of splitting the node-set into constituent clusters, which limits and decreases the number of possible solutions checked by the optimiser, consequently driving down the runtime .
After revision:  The improvement of runtimes with the Recursive-DBSCAN method is because of splitting the node-set into constituent clusters, which limits the number of possible solutions checked by the optimiser, consequently driving down the runtime .