Robust and muscular?? And they would know that how??
By the way the muscles/tendons were attached to the bones.
IIRC, muscles and such leave marks on the bones.
The fact that the bones were probably quite dense for somebody of that height and gender says that the person led a very physical sort of life, which leads to them being very strong, as compared to somebody who leads a relatively sedentary life.
They can project her body type (slender, delicate or stocky and robust) by the size of her bones, although I would quibble about calling a 5’4” female an “Amazon”. I suppose that depends on the size of the male skeletons of the time.
You can tell the strength of the muscles from the condition of the points at which they attach to the bones.