The VCF On-demand precheck reports an error 'Network latency' on vSAN stretched clusters but no such problems are reported by vSAN Skyline Health.
This is a regression in VCF 5.0, 5.0.0.1, and 5.1. VCF On-demand precheck expects the 'Network Latency' check to be run by vSAN Skyline Health Checks, however, for stretched clusters this check is replaced by the 'vSAN stretch cluster site connectivity' check. This results in an error incorrectly reported by the VCF On-demand precheck.
Currently there is no resolution. This will be fixed in the future release.
This is a false alarm. Ignore the 'Network latency' errors for vSAN stretched clusters.