Nothing has shown more muscle growth with GLPs, but muscle protective and endurance improvements have been demonstrated. These effects become more pronounced with age, I assume, because as natural GLP production declines exogenous GLPs have more empty receptors to hit.
Muscle tissues are rich in GLP-1 receptors. When activated, muscle fiber loss is slowed, and GLPs also stimulate microvasculature growth in muscle, improving endurance.
The issue of lean mass loss on GLPs is entirely due to insufficient protein intake and often, a lack of strength training.
But all things equal, on a cutting cycle, same diet, same amount of training, GLPs should promote more muscle mass preservation than without.