Thanks for the reference to that point in the video where she discusses dark hair. She says they are testing that, but doesn't say that it prevents the thing from working at all. I seriously doubt that it would prevent it from working.
Basically, whatever structure you put in front of a laser beam to scramble up the light, and absorb it in certain places -- no matter how mangled the "exit pattern" (the light you get out on the other side), you can invert that process. In other words, by recording the light coming out the other end, you can work out the pattern (basically, just record the light pattern, and project it back in the opposite direction), so that if you shine that pattern into the structure, out the other end will come a straight-line laser beam. Jepsen demoed this a while back, on-stage (begins 5 minutes, 45 seconds in):
She made a "brain laser" -- they figured out the pattern to project into a brain so that a straight-line beam comes out the other end.
This is counterintuitive to most people, I think -- they don't imagine you can unscramble the light to such an exquisite degree through an object so complicated as a brain (or, rather, the light re-focuses to a beam as it passes through a brain)... but you can.
Note, also, that the brain not only scatters, but also absorbs.
Now, what if you put a skull and hair on that brain? Do you really think it would make a difference? The hair would absorb some more of the light, and so might the skull. Furhtermore, there are so-called "snake photons" that can bounce around in the region between the brain and skull over a great length. But all can be rectified in the end -- it all a deterministic process.
The main thing you have to worry about in order to pull off this feat is the "speckle decorrelation" time: "speckle" refers to the little grainy interference patterns of laser light. What happens with an object like a living brain is that blood moves around and changes the pattern -- very quickly. And so, if you want to back-project light to make a brain laser with an actual living brain, you need to be able to bounce the light back quicker than the time it takes for the brain to change that pattern. It turns out to be 10 microseconds! So long as you operate within that window of time, you can do it -- no matter how tangly the hair.
Let me add another thing, unrelated to what you wrote, just to mention my point of view:
As far as "reading minds" go, the skepticism on that is way overblown. The main reason it is considered "hard", and why progress has been slow, is the fact that teams are operating with only very small amounts of data. When you have only very little data, you have to be a lot more clever, and throw as much neuroscience knowledge at the problem as you can. But if you an abundance of data, you can just train a machine learning model to figure everything out for you -- and it doesn't even have to be that complicated; a high school kid with access to Google Colab (to write and run Python programs) could do it.
In fact, there was a recent Medium piece by the founder of Paradromics on the misplaced skepticism, centering it more on managing expectations and controlling hype:
With high-profile entrepreneurs such as Elon Musk and Mark Zuckerberg getting involved in the field of brain-computer interfaces, it is fair to say the technology is receiving its share of hype. Many scientists who have devoted their life’s work to creating meaningful and lasting advances in BCI are justifiably concerned about managing expectations to ensure sustained public support. It is in this context that several leaders in the field have expressed, in some form or another, the following reservation: We do not understand how the brain works; therefore, we are far away from advanced BCI applications. I believe this sentiment, though rooted in good intentions, is both reactionary and misguided.
First, though we don’t yet have an all-encompassing theory of mind and consciousness, neuroscientists know a lot about the brain, neurons, and neural coding. We know more today about how the brain works than Jenner knew in 1796 about how the immune system works. Critically, we know a lot about the localization of sensory and motor functions within the cerebral cortex and how brain activity in those areas reflect their respective functions.
More importantly, building useful BCI technology does not require a perfect understanding of the brain. Arguably, it doesn’t even require a good understanding of the brain. We know how to record brain signals to control prosthetic arms and computer cursors. We know how to feed tactile data into the brain for prosthetic feedback. We know that stimulating the visual cortex has enabled blind patients to “see” visual patterns. While it is true that BCI could be enhanced by additional neuroscience research, waiting until we have a complete understanding of the brain before building BCI-based therapies would be no less folly than if our predecessors had withheld the polio vaccine until the sequencing of the human genome was completed.
The esteemed neuroscientist Konrad Kording concurred, and went further and said that "understanding" may not even be necessary at all:
Matt Angle nicely makes the point that to have well-working BMI systems there is no reason to first understand the brain. Imho, it may not even really be helpful.