We need to document a significant change in disk ordering / symbolic naming behavior in 4.13. I do not believe this impacts upgrades, but is important for fresh installs.
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With RHEL 9 kernels, the symbolic sdX disk naming can often change across reboots. This can cause RHCOS install issues where the 2nd boot can't find sysroot if a symbolic name like "/dev/sda" was used as the install device. The general recommendation for device parameters, including any specific disk reference, e.g. for LSO/ODF installs, is to use a persistent naming option such as /dev/disk/by-id or WWN. 

This could require an adjustment to some existing automation since some sort of inspection may be needed to collect the install device by-id for each node. IPI and AssistedInstaller provide the rootDeviceHints option, for UPI it can be passed through the 'coreos.inst.install_dev' RHCOS install parameter. 

4.13

often if non-persistent naming is used

1. Fresh install 4.13 on baremetal system w/ multiple drives

Something like "sda" is no longer a reliable disk name

Documentation about this behavior change