Thanks for the link! That is an interesting article, and pretty well sums up the available literature.
I think we can safely assume there is an ideal size crank arm for each rider, and that power or efficiency or something will drop off dramatically when using cranks that are too short or too long. But I have never seen test data that clearly identified what is "too short." I assume that even for tall riders it will be much shorter than 165 mm; but that assumption, along with all the other assumptions, really should be tested.
Its pretty well known that if you have short cranks you can increase your cadence, not unlike what happens in a reciprocating engine.
I don't think power is the big deal here though. There have been some studies that show that the power output only varies by a few percent but the internet being what it is, I can't find the studies that I read ten years ago. The big deal is actually joint injury. This probably won't happen on a shorter ride (600km) but if you go on a longer ride its a common problem which shorter cranks do address. That is how I found out that I can't do 175s- I feel it as soon as I get on a bike using them. If I try to go longer distances (500 miles over several days) I get knee problems. Going twice that distance with 170s no problems at all. A person well-versed in this is Mark Stonich of Bikesmith Design- he's been shortening cranks for many years.
My GF is 5'3" and has the shorted frame Trek makes- but amazingly it is equipped with 170s which seems obvious are too long. She's had knee problems for many years and so doesn't do longer rides anymore. I pointed out the issues with longer cranks and she got a shorter set- no more knee issues! I know its anecdotal, but this idea has been around a long time. However, in doing a search I ran across this:
https://www.stevehoggbikefitting.com...gth-which-one/
Which has some very interesting comments, very nicely explained.