Self selection bias seems to be happening in a lot in exercise science articles in health magazines for a long time. For example you have Brett Contreras measuring EMG activity on his own body and his friends and then arguing which exercises are effective. Come to think of it all trainers have been doing Cressey, Robertson, Poliquin, etc… How can exercise science claim to be a science when its layered with this bias.
Outside of basic human anatomy (which is scientific) the value of an exercise (which is not scientific) is a subjective call and therefor there can’t really be a uniformity of effectiveness of an exercise. All trainers seem to rely on their personal experience for effectiveness of exercises or are trying to carve out niches for themselves but by adding in studies to back their claims they are just defaulting to expert bias.
My point being it appears to judge the effectiveness of an exercise time should be the filter used not EMG or personal experience. What has worked for the average will mostly likely continue to work (Squats, Deadlifts, Presses, Pullups, etc…) New exercises should be looked with skepticism as should the trainer who espouses their value as time hasn’t determined their value or not.