That's adorably quaint. I wonder if djb still believes that's the case?
There is no good reason to give it even a gigabyte of ram, let alone many multiple gigs.
I would say the notion that small binaries working together (the unix way) would still allow him to believe to be the case.
Various other systems also limit with things like /etc/login.conf on FreeBSD. There is also /etc/security/limits.conf on Linux for non-systemd stuff.
Limits for memory usage/open files/things of that nature are natural. You don't want one runaway process to cause the rest of your system to OOM.