While I can’t say much about the specifics of Japanese health and nutrition, I’d argue it confirms the general tenet of dietetics that restrictive dieting is largely not good for you (and isn’t easily maintained either).
Eating too little (or unbalanced) taxes your metabolism to free up glucose from your organ stores and store what it has, plus running the risk of nutrition deficiencies too. Plus eating too much also has it’s obvious risks.
I think in regards to keto, the risks of high fat diets are independent from the effects of ketosis. You still run the risk of CAD, obesity, high cholesterol and the issues those bring. (It raises LDLs but lowers triglycerides according to a paper from the ACC, they and the AAND are not convinced one way or another it seems on if keto should be recommended)
I think a big part of it is the mindset that college education should train you to do a job, rather than provide a knowledge based on which job-specific training can be built upon. I think this is dually precipitated by employers not investing in training/educating their employees anymore, and outsourcing that cost to the employee, but also the issue of students who throw a fit about taking class X because they're going for a degree in Y (I see this a lot with science/engineering majors when having to take classes in the humanities).