I haven't seen that happen personally, but I've only seen recently their disclaimer about potentially adding shipping fees upon final release.
"During pre-order, the shipping fee is estimated. Final fee applies when paying the balance. Shipping methods may change based on final item's size and weight."
I don't recall this with previous orders with their sister site ShowZStore where I typically order the majority of my transformers from. But, I did notice it when I PreOrdered the recent InArt Ron and Hermione.