This is understandable. Any artist that is involved in the creation of a character that has already been done by another will want to know all the details of what went into that other piece, like the beautiful SSW Sauron.
Most likely, it is reference primarily to aid decision making for what not to imitate, like the pose, so that each statue will have their own unique look.
As far as the skinny leg issue, Sauron's legs are actually on the thin side in reality. I have a lot of imagery from the FOTR set that confirms this, so the SSW piece is very accurate, BUT one of my main suggestions to SS with the 1/4 scale Sauron was to bulk him up more, especially in his leg armour
JV