More sets, more reps and 6 days in the gym will quickly lead to overtraining and loss of muscle mass and strength. (fitnessandpower.com)
The other mistake is to go out guns blazing and do too much volume which can also lead to overtraining in the long run. (fitnesscrest.com)
That MO has some relevance to gaining size and strength because you do have to keep overloading your muscles to keep making gains, but it can easily lead to overtraining if you don't know what you're doing. (legionathletics.com)