Actually, this entry is under ごとく since the 〜かの before it can be seen as a noun phrase, 何万年も前に戻ったか(noun phrase) ＋ の ＋ ごとく
Actually, it sounds similar with 〜かのような, only thing is now since the following phrase is either an Adjective or Verb, it becomes 〜かのように. And also, ごとく is a classical word.
I agree. The かの of 〜かのよう（に） might need special explanation for those at a lower level who aren't familiar with these constructions, but once you've reached level 1 and presumably long-since mastered 〜よう（に） and 〜かのよう（に） I wouldn't have thought this required any further mention once the entry for ごとく had been read; certainly not a seperate entry.