In case of high load on a system (many sessions, lots of HDD_READ) the database executes some expensive management operations to cope with the load (heap memory resize, DBRAM defragmentation). For those operations all running sessions on a node need to stop for a short time until the operation is completed.
Sometimes a session stops very slowly which defers the execution of the management operation, and hence, defers all other sessions as well. Usability impression in such situation is often not good.
Session stopping has been optimized to have all sessions stop in a shorter time. The time waiting for management operations will be reduced, and hence, the usability impression in load situations improved.