Drake Crests are Normal gear, not “top tier”. Additionally, all content is equal in terms of time and effort. The Drake Crest Chest should be available for the Cocoon as the quest for it is weekly.
It’s simply not worth the time and effort to do the Dreamsurge for 15 Whelpling quests when you can get the same results flying around the Dreamsurge zone for 5 minutes. As you even mentioned, you can get Drake Crests just farming Dreamseeds, so the entire “farm world quests” argument is nonsense.
If the intent is that only the Whelpling Crests are available for the cocoon, then so be it, it’s another time sink we can avoid. And if that’s the case, it needs to be clarified and the notes need to be updated. If not, it needs to be fixed.
That said, I do doubt that it’s intended to get Wyrm Crests this way. However, getting Drake Crests is perfectly reasonable.
Edit: Clarification. I should have my coffee before responding. My brain was thinking Drake Crests while my fingers were typing Wyrm Crests.