> Our bodies are really good at providing exactly the amount of muscle we need for our daily activities

That is exactly the risk. Our bodies are really good at it. But we are taking drugs that may change what our bodies do. Even a small bit of extra heart muscle loss may push as below where our bodies would have left us naturally. Is that dangerous? Are there people who need to worry about it? How do we know whether or not that should be a concern? It raises questions, and is worthy of discussion, even if we do land at answers that say it is an acceptable level of risk.