SELinux is almost 20 years old now. Most software that runs on Linux is well integrated into SELinux by this time and Domino should be, too.
I would add that I've been routinely ignoring that instruction for quite a few years now and never seen an AVC Denial in CentOS nor RedHat Linux Enterprise. Maybe all that needs to be done is some testing to validate that installing and running Domino on Linux with SELinux in Enforcing mode does not cause known problems and is, therefore a supported configuration. This would enhance Domino's reputation in Security. See Promote Domino as the most secure thing on the planet.
So to clarify, what I'm asking for in this "idea" is for Domino support for SELinux by HCL testing installation and runtime of Domino with SELinux in Enforcing/Targeted mode.
If no errors are observed, then the documentation should state that this is a supported OS configuration.
If any access issues to system objects/files (like the mongodb example in my comment below) occur, then the fix would be implemented in the installation routine or alternately documented in the installation instructions and the knowledge base.