No. Read what a Cybertorso and Cyberskull are.
From Core Rulebook, page 455:
"Cyberskulls and –torsos are included in the “cyber- limbs” category, though they are in fact shells rather than full replacements (or actual limbs)."
So if you have a cybertorso, you still have all of your internal organs, bones, connective tissue. Even if we assume that the 'outer' musculature is replaced, they might still rely on the strength of the connective tissues to keep from wrenching your spine out of place, or snapping tendons along your rib cage or whatever. Thus, even though you have really strong and agile parts, they are limited by these aspects of your natural body.
And yes, you paid essence, but in return you get additional strength, agility, armor, smuggling compartments, and all the other stuff yu put in. What you DON'T get is a higher physical limit. Unless you actually build those up.