The effect mentioned in the article I believe is to be noted after the fry has grown.
I have seen this too many times in juvi/adults I have raised without MB at all!
I actually have 2 small(very yellow looking) gbr in my 55(aprox4-5 months) that are never off bottom.
They are not well fish.
I have also seen adults do the same.
Some after a full year of good life and health?
It is clearly not a contagious issue so I try to keep them for observation.
Before I feed them to Mr. grouper or eel!
The article is definitely describing what I see with out MB over time.
Mind you this is a very small percent but odd only some out of whole breed of fry?