Ok so I guess that's a mistake of my textbook.. "Holding patterns are to be flown at the following speeds :"
Then it proceeds to give a table of speeds including the M0.83 of above.
Another surprising point is that the turbulent conditions speeds are higher than the normal condition speeds. Why would you be allowed to go faster in turbulent conditions ? To go through higher variations of VRTG and get past VNE more easily ?