That’s not really comparable. Retatrutide shows relevant fat-loss effects at doses well below 12 mg. Tesamorelin doesn’t have the same kind of evidence for lower doses.
If someone is aiming for the effect shown in studies, then the studied dose matters. What you do with that information is up to you.
Also, Tesamorelin’s fat-loss effect appears to be more visceral than subcutaneous, not general fat loss. Since its a GH/GHRH the lean mass is probably just the result of water-retention and is measured on these type of scales as lean mass