Completely false. The more muscle you have, the greater amount of buffer you have to protect your soft tissues. Whe I got a partial ATL tear several years ago, my legs were smaller than they had been when I was squatting 400+. When I felll, more torque came to my knee because my thigh could no longer protect it and mitigate the tension.
Now, if you want to argue that more muscle = more weight or greater speed and those things increase injury possibilities, i.e. you are more likely to get injured falling while going 12 miles per hour than 8 - that could be true. Basically muscle protects.