Exactly.
The mucin deficiency is caused by too little carbs and protein in one's diet.
It doesn't matter if the diet is raw, cooked, based upon pork or lamb - these drawbacks are the same if the diet is unbalanced.
Raw ZC is better than cooked one, but still harmful.
I have to admit although I've done some research on OD in the past, I've never heard of these kind of dangers from a low protein/carb diet. I'm curious how you know for certain that many of these issues are not exacerbated by the nature of the foods included. I mean as you started to list, and with traditional ketogenic diets (neither of which are actually ZC) the selections are pretty over the top in terms of daily consumption.
it also seems to imply just doubling the already extremely low protein amount could be all that is needed, although it suggests additional carbs would be preferable. FWIW this 'new' protein amount seems to be on average still lower than
most people here following ZC or VLC and consciously monitoring their protein intake somewhat.
I'm definitely one of those VLC folks who really digs on carbs even if can avoid them for weeks without craving or other issue. I vibe more with omnivory as an identity and concept and I would probably add more carbs if I felt good doing so and believed it to be the best for my long term health. My strategy is to get the largest variety over the year (including seaweeds, fruits, wild plants, organic greens, various mushrooms) from a nutritional standpoint, and spaced out enough to enjoy the metabolic or healing advantages I presently believe associated with VLC. I do heed alot of the concerns at times tho, particularly when in a pinch it doesn't seem I can handle certain types of foods well or in abundance. I guess coming from raw veg days where this is a sign of 'cleanliness' I become skeptical when types raw natural food cannot be switched on and off alot easier.
anyway, don't have a solid opinion but those are my thoughts. I do think the title is a bit off per that study but its a good conversation to have nonetheless in relation to these macro nutrients.