[JdeBP]

That is not actually true. It is of course parsed by a shell, not by a shell script, which is indeed an "ELF blob".

Moreover, that shell is, on some operating systems, only one of the parsers. OpenBSD, for example, introduced a rule a few versions ago that rc.conf is not shell script. It is a set of key=value assignments that can be written and read by other programs too, not just by a full shell parser and not requiring a shell script parser.

One such program is rcctl. Another is FreeBSD's sysrc.