(Author here) Because it was absolutely unclear at that time yet, that an older kernel version could mount the XFS partition but the newer kernel versions could not (this only came up during the post mortem/RCA later). Furthermore the clock skew and mon_host issues gave us a wrong picture of the situation. (Also as the hosts are running as hypervisor systems, the kernel version should ~match with the environment (Proxmox/KVM), so there might be other/unclear risks with running such a setup.)