Indeed, it seems the Netherlands study separates whether or not you can then further trade the items to determine if it's gambling or not. Therefore, some games like Overwatch don't fall into this category.

Regarding trading card games, they are indeed awfully closed to gambling; and they are in fact the main defense of the game publishers, arguing that this is just a "collect and play" type of game, and isn't gambling.

But isn't the interactivity, the bells and wistles, animations of the lootbox openings closer to addictive reward patterns than just opening a plastic card booster pack ?