The purpose of the KB is to understand minimum system requirements to perform vCenter Reduced Downtime upgrade before actually starting the upgrade.
If the minimum system requirements are not met the vCenter upgrade may fail.
VCF 5.2.1
The VCF on-demand pre-checks for vCenter are just a part of all the checks we conduct. Additional checks are also carried out during the upgrade process. This KB can be used to identify the minimum system requirements before starting the upgrade process.
The System requirements can be referred from here : https://docs.vmware.com/en/VMware-vSphere/8.0/vsphere-vcenter-upgrade/GUID-752FCA83-1A9B-499E-9C65-D5625351C0B5.html