It depends on the sport, he could get bigger and still keep abs, but it would not benefit his tennis play. I am not sure what you think by massive exactly, but people can be pretty mascular and have abs without steroids. If you train for estetics and are crazy about your diet, you can look quite big. I guess what influencors do not communicate properly is how mich time, effort and money it takes to achieve their phisique, it is their full time job to look good. Average person can invest few hours per week at best into that. It is much more important to be health and fit than for your abs to show.