The problem is it is bad. People aren't just losing a proportional amount of muscle to fat mass to keep a good ratio - rapid weight loss is more catabolic towards lean body mass than it is with slower weight loss.
And most obese people are below optimal levels of total lean body mass overall even before this - their leg muscles being larger than an untrained person of the same height and an average weight does not mean that their leg muscles are of optimal size, much less the rest of their body.
Sarcopenia is a real risk for any obese person who is rapidly losing weight and GLP-1s are no exception.
When people read "muscle loss" they think "oh it's going to make me weak and feeble".