If you dont resistance train, any weight loss regimen will cause a loss of lean body mass, medications aren't different from an "organically" achieved caloric deficit. Training and size of the deficit as well as genetics heavily shift the proportion of adipose to lean tissue (which includes water) lost.

So far as i know, the signal that glp1 agonists are particularly worse for lean mass retention isn't strong enough to claim that they're worse for muscle mass retention than normal dieting.