For ostree and bootc installs, the /boot partition should be mounted ro to align with how ostree and bootc installs outside of Anaconda are documented and work.  However, if the /boot partition is created (via reqpart --add-boot) then the partition is mounted rw.  This has lead to a customer bug report which is tracked on RHEL-66155 (along with a separate issue that the install fails when there is no separate /boot partition).

•  https://issues.redhat.com/browse/RHEL-66155?focusedId=27560684&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-27560684
• https://issues.redhat.com/browse/RHEL-66155?focusedId=27890908&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-27890908

To fix this, we would need to make sure that the /boot partition that we create is mounted ro after the install.