dbltoe:
Im' pretty sure it's a feature.
If you are picking it up in the store or shipping for a flat rate of $5 per, why does the customer need to know the weight? Is store pickup liable to be something that requires a Ram truck vs a VW?
When you sell Flat rate the seller still has to ship the product. When you go to the Order Page and no shipping weight shown it is a little difficult to guess weight or makes it slow to weight every order. If it is shown on order page then the shipping label program will import and print label same as USPS, FedEx, or UPS. I know the weight is calculated it is not shown on the Invoice or Order Page and used to be on 150 Green cart.
I don't use weight on Store pickup but there could be some products as you said would give customer information bring truck or would fit in VW.
Since the information is not shown on these two I would guess the other available shipping methods weight would not be shown.