Are my cards insured while they are at the grading company?
In short: Cards travel insured when I ship them. While the grading company holds them, its own submission terms govern, so check those terms and your own coverage for anything valuable.
Outbound shipping through the hub is insured and logged. Once the grading company signs for the package, the cards are in its custody and covered by whatever its submission terms say, not by me.
For valuable cards, your own collectibles coverage matters more than any shipping policy. I do not sell insurance, but insurance documentation gives your agent the inventory and valuation needed to schedule the collection. The outbound photographs from the hub also give you a record of each card's condition before it left.