Process substitution $(...) gets executed first, so it cannot be passed into a find -exec command.
Solution
dirs_acl_cmd='nameq=$(printf "%q" "{}"); reset_acl '"$dirs_acl"' "$nameq"'
fd -j $THREADS -u -td . $vo_dir --exec bash -c "$dirs_acl_cmd"Process substitution $(...) gets executed first, so it cannot be passed into a find -exec command.
Solution
dirs_acl_cmd='nameq=$(printf "%q" "{}"); reset_acl '"$dirs_acl"' "$nameq"'
fd -j $THREADS -u -td . $vo_dir --exec bash -c "$dirs_acl_cmd"