The generators have a lot more value to being in stock before or during the storm than after. When I bought mine, I had to drive two hours away to a Lowes, because they were out of stock in my county. If the local Home Depot had one, I would have just bought it there. The person buying and returning it is not only costing them a fraction of the cost (credit card fees each way); but also actual sales.
On the other hand, I think that in general, the relaxed Home Depot returns policy helps them. I often take advantage of the ability to buy multiple sizes of things, extras in case I mess something up, and then when I'm done with a project go back return the excess. If you use a credit card, that is even easier than keeping the receipts, they swipe the card, scan the stuff, and it goes back automatically. I find this easier, because I always have my card; and there is no need to have however many receipts that the items were originally bought with. And for very small stuff that I could conceivably use in the future, there is a decent chance I won't bother returning it anyway.
On the other hand, I think that in general, the relaxed Home Depot returns policy helps them. I often take advantage of the ability to buy multiple sizes of things, extras in case I mess something up, and then when I'm done with a project go back return the excess. If you use a credit card, that is even easier than keeping the receipts, they swipe the card, scan the stuff, and it goes back automatically. I find this easier, because I always have my card; and there is no need to have however many receipts that the items were originally bought with. And for very small stuff that I could conceivably use in the future, there is a decent chance I won't bother returning it anyway.