I'm procrastinating on my homework, so I actually sat down and read the study in question, and this is why we need to question pretty much everything that we read. I think the person who posted this on the other board misinterpreted the findings.
The phrases in bold come from two different sections and are referring to two different things...I'm assuming that they just copy and pasted that stuff together to make their own point.
Firstly, "Coconut oil performed better as a pre-wash rather than a post-wash conditioner" was definitely not the overall finding of the study. The point of the study was to see how mineral oil, sunflower oil, and coconut oil work to prevent hair damage. The overall finding was that for damaged hair, coconut oil was best because it can penetrate the hair strand (due to the arrangement of it fatty acid bonds and it's molecular weight), and that sunflower oil and mineral oil are essentially on the same footing because neither of them can do that. I can't copy quotes because it's coming out weird, but the overall finding can be located on the first page, last paragraph of the synopsis. So that's that....coconut oil definitely penetrates the hair. If your hair is crunchy with it, your hair just doesn't like coconut oil or it's gone and frozen on your hair. Or if you've been using coconut oil problem free and it suddenly started acting up, then maybe it's doing its job a little too well, and you now have a problem with protein overload.
But going back to coconut oil performing better as a pre-wash rather than a post wash conditioner, that was referred to in the section where the scientists were testing for protein loss, not the oil's ability to penetrate. The study says that if you are using coconut oil to avoid protein loss, then it is better to use it as a pre-wash than a post wash. This is because hair loses most of its protein from the inner layers of cuticles as they open and shut. If you use coconut oil before washing, then it can sink in and lubricate the inner cuticles and make it easier for them open and shut stress free. The study also assumed that people wash their hair with hot water, and they used boiling water for their experiments. If you don't use hot water in your regimen, then this may not even apply to you, because your cuticles wouldn't even be opening so much. But anyway, using it after washing is less effective because by then, the cuticles have already opened...putting oil on them at that point is kind of a little too late. If you look at the chart, it will still be good, but just not as good as putting them on before. All of that can be found on pages 11 and 12.
And as for, ""In post-wash application the oil film is on the surface with no penetration into the fiber", that quote wasn't even about coconut oil specifically. It applied to all oils in the study and came from the section where the study talked about water retention index (WRI), or how much water is in the cortex (how swollen it is) when these oils are applied pre-wash and post wash. According to the study, for damaged hair, you don't want that much water in the cortex. If the strands are constantly swelling and shrinking, your cuticles are under constant pressure and stress, which only damages them more.
The study says that when it comes to reducing the WRI, it is better to apply your oils before you wash instead of after. This is because some of the oil (the study called it "oil film" or "residue", and all oils make it) sits on top of the hair, and keeps moisture from getting out. Lol, we call this sealing.
But if you apply your oil before you wash, then it's there when the cuticles open, and it's a possibility that some of the hydrophobic molecules can get through the cuticles and keep too much water from getting into the cortex. But this part is full of "mays" and "possibles" and "must bes", so it's clear that the researchers aren't even sure of how that really works.
The bottom line is that if you don't want your cuticle all waterlogged, then pre-poo with oils. If you look at the diagram, then all the oils are effective to an extent. But coconut oil is obviously the most effective, as the hairs that were treated with it have the lowest water retention index. This is presumably because it is easier for coconut oil to penetrate the hair than it is for the other oils, so it's easier for it to keep water out. And all of that is on pages 14 - 15.
The only thing I see this study saying is that coconut oil is magical stuff. Which many people knew already. And I'm sorry for the novel lmao, but someone should tell that other person to sit down. I hate when people twist stuff up to fit their own conclusions or beliefs or whatever.