I shared a few emails with Darius 18 months ago when working on a profile of DeVries which aimed to highlight Mike's career accomplishments (of which Cape Wickham was undoubtedly one). Without sharing too many details of what was a confidential email, it became clear in reading Darius's first message that the story was worth way more than my 1,000 words (the Cape Wickham part was probably only a quarter of that) was going to cover.
I wince a bit now when I read the article given Darius's post and new details that have come to light. I don't suppose there is much I can do about that, but there it is.
One thing I will share is that Darius wrote Mike did "much of the routing" which seems to run contrary to what he said in his PlanetGolf post where he wrote "Duncan, Mike and I then produced the final routing."
As others have said here, I think design credit should ultimately go to the person that routes the course which, if the words in Darius's email are true, was Mike. If, in fact, Duncan Andrews, Darius and Mike worked equally on the routing (how would you calculate something like that?) then you might have to consider who did the most work on the individual holes once the routing was in place or, alternatively, name all three as co-designers.
Again, as others have mentioned, I don't think it was in Darius's best interests to post his 'Inside Story', and it was probably better coming from someone else. I totally understand him wanting the world to know the truth (at least what he considers the truth) though. Then again, how many people besides Duncan Andrews and Andrew Purchase really know the whole truth? And, given he has chosen Darius for his Kangaroo Island course, wouldn't Andrew also want the world to know how much Darius contributed at Cape Wickham? As for Mike, if he's asked about it my guess is he'll give as close to a "No comment" as he can without being rude.
Bottom line - if the situation calls for a quick response, I'll continue to call it a Devries design. If, however, I'm discussing the design story over a long lunch with someone who cares, I'll certainly be mentioning what Darius did (or claims to have done).
Funnily (actually, it's not very funny at all), before all this broke, I included the 18th in a '21 Great Holes from the 21st Century' article, saying "...architect Mike DeVries, together with Australian designer Darius Oliver...".
I'm not sure what that distinction means exactly (I notice there is a newer thread on the 'Architect v Designer' question), but it worked for me.
Lastly, all the best to Cape Wickham and the rest of the island/state. I sincerely hope it survives the pandemic.