Yes, what does one have to do to qualify as an expert in bodybuilding? I suppose there are many levels. If you have made good gains in a gym and people compliment you on your size I guess that is one level of being an expert. Hence, most on Getbig qualify.
The next level requires that a person has read the literature and/or has vast experience training in the gym. At this stage you can argue with others about training protocols and you will usually be able to assess whether various methods have merit or not. It also requires experience at doing these other methods. That is the main way to know what is effective and what is not.
The third level is formulating a new theory of hypertrophy along with training methods needed to get there. This theory must be new and bold. It must explain things that haven't been explained before.
The highest level is obtaining a PhD in hypertrophy and perhaps doing original research in the area to demonstrate hypotheses. I know of no one at this level.