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vSphere 6.5 DRS and Memory Balancing in Non-Overcommitted Clusters - VMware vSphere Blog

basically the default methods doesn't use 100% of the commited memory metrics, it uses the active memory metric to balance the memory acutally in use. It mentions a setting you can enable to have the commited memory spread more evently, but its more likely to trigger memory reclamation if you over commit your hosts.