As black3r mentioned (https://news.ycombinator.com/item?id=46686096), it is likely rearranged by systemd, therefore only non-systemd glibc distributions are affected.

I would hazard a guess that their test environment have both the systemd variant and the Unbound variants (Unbound technically does not arrange them, but instead reconstructs it according to RFC "CNAME restart" logic because it is a recursive resolver in itself), but not just plain directly-piped resolv.conf (Presumably because who would run that in this day and age. This is sadly just a half-joke, because only a few people would fall on this category.)