My wife has worked for State Farm for about ten years. The estimator will want to write as high as claim as he can to avoid adjustments. When your vehicle goes into the shop for repair anyhe did not write it high enough to cover repairs and the shop has to request an adjustment it reflects poorly on the estimator. Most major insurance companies are this way now.
If you want to get paid on add-ons you will need a combination of receipts and or examples of cost (price of similar modded vehicle)
Also worth mentioning, if they give you a repair estimate and you feel it is low and you start asking for more money before it is even in the repair shop, there is a good chance you will get canceled on your next renewal, and that can make it hard to get new insurance. I fit is a total loss, it will be priced through the total loss dept and they will give you a check for NADA value plus tax
Their duty???? Dime stor insurance that relies on customer premiums to sustain the business, perhaps. One of the big 7, not so much. However I have heard some bad stories about Geico. There is a reason State Farm and Amica have the highest Cust sat rating by a massive margin over all other companies.