Final answer:
The statement is false; VMware Update Manager can remediate multiple hosts in parallel in a vSAN cluster if it is safe to do so, considering vSAN health and data availability.
Step-by-step explanation:
The statement that VMware Update Manager (VUM) remediates hosts that are part of a VMware vSAN cluster sequentially, even if you select the option to remediate them in parallel is false. VMware Update Manager provides the capability to perform host patching and upgrades in a way that integrates with vSAN and respects its requirements. When updating or patching hosts within a vSAN cluster, VUM can perform rolling remediations that will evacuate one host at a time and perform the necessary updates while maintaining cluster resilience. However, VUM does consider vSAN health and data migration aspects before proceeding with updates. If you have selected the parallel remediation option, and VUM determines it is safe to do so, it can remediate multiple hosts in parallel, keeping in mind the need to maintain data availability and vSAN cluster redundancy throughout the process.