Interesting. I suppose you can expect steroid enhanced muscles to tear more easily because muscles are not all muscle filaments but many sorts of support tissue that may not be as receptive to androgen as muscle cells themselves but tendons and other types of tissues that make the muscle more durable against internal and external stress. Muscle growth occurs when wear and tear occurs at a microscopic level and when the body overcompensates for that. When you speed up the growth process artificially, it shouldn't be surprising that not all of the tissues in a muscle may keep up.