This might seem completely surprising considering how closed off GW may seem to their customer base, but there are good, logical, business reasons why they do almost everything.
For instance, GW doesn't focus on forums because of how polarizing it/we can be and how small a portion of their gamer population it is in comparison to the groups of new customers who spend the most money.
Conversely, if we consider the cost to GW to replace a sprue, blister, or whole plastic vehicle kit - the benefits completely out weigh the costs. First if you have any sort of proof of purchase to ensure you have just tried to scam them, then they have already made profit from the transaction. Second, you paid top pound/dollar/euro for injection molded plastic/resin (or formerly metal) formed into their proprietary shape. 6 oz of plastic and shipping costs are likely already paid for by the profit from the first model.
Ultimately, the cost for sending a new model to a customer is minimal compared to the good will it generates.
I don't think this should be all that surprising. But do I think recognizing that AND managing to be pleasant and swift about meeting those customer service needs is impressive.