For that particular kernel you are running, maybe one or all of the “y” values was, instead, configured to “n” (intentionally, or perhaps as an oversight during configuration) so the check, and the associated warning, is skipped.
I am using 5.10.27 kernel for both a2-runit and a2-full. As you suggested, I examined the config-5.10.27-antix.1-amd64-smp of each of the a2-runit and a2-full. Below, I am displaying any lines that contain the selinux keyword. As you can see, they are identical. Before using the selinux=0 command to disable the selinux, a2-runit would not display the selinux policy.33 error message, but a2-full would. With respect to the config-5.10.27-antix.1-amd64-smp of each of the a2-runit and a2-full systems, the selinux parameters appear to be identical.