RHEL is an LTS distribution in which each major version is comprised of multiple minor versions, supported in parallel for a given number of months. Users are free to choose when and how they switch from one minor to another. At the time of writing, supported minors in RHEL-8 are 8.1, 8.2, 8.3 and 8.4. The following document gives more details on exact support timelines for RHEL-8:
MariaDB Server packages are built on the latest version of RHEL, 8.4. A dependency on a particular system library, libsepol, is set up not only on its version but also on its release number. Release numbers for a package in RHEL typically change in every minor, so this means that our MariaDB Server package can only be installed on RHEL 8.4 and not on any previously supported minor. This creates issues with users who prefer to stay one or two minors back in their RHEL version in order to avoid bugs (to which RHEL is anything but immune).
To avoid this, MariaDB Server packages should only require a suitable version of the library and not include in the dependency (the "Requires:" line in the spec file) the release number for the library.
Example (from RHEL-7 to which this also applies);
It is pretty hard to believe that we depend not only on libsepol-2.5 but on this exact RHEL build number 10.