As not being mentioned in it, /hurd might be considered not compliant to the FHS. It is FHS compliant. First, even if it is not the prefered solution, nothing prevents a distributor from adding things in / that are not explicitly described in the FHS. It is the prefered solution. Second, the two possible solutions for the translators in /hurd would be /sbin (and /usr/sbin, but /usr is a symlink to /) and /lib. Those are not possible solutions.