I used https://build.funtoo.org/1.4-release-std/x86-64bit/intel64-skylake/stage3-latest.tar.xz. Of course that's changed since. I used the version current around September 25 or 26, which is no longer available to download.
The current version—stage3-intel64-skylake-1.4-release-std-2019-10-11.tar.xz—still has separate /usr/lib and /usr/lib64, so it seems that would still cause this bug.
The stage3 tarball /lib is a symlink to /lib64, though (which is not the case on my system).
So should I move everything from /lib to /lib64, and everything from /usr/lib to /usr/lib64?