Mario Golf: World Tour has taken Nintendo into a completely new realm of DLC -- Season Passes. Although they have dabbled in the practice for some time now starting with Fire Emblem: Awakening or New Super Mario Bros. 2 (depending on the region), Season Passes generally weren't a thing until now.
Thankfully, the folks over at Nintendo Life have confirmed (in the UK anyway) that the Season Pass will not consist of "on-disc" content. In other words, these downloads are legitimate content packs, weighing in at 489, 447 and 138 blocks. Once again, Nintendo is being completely fair with their DLC methods.
Mario Golf: World Tour’s DLC Isn't Locked Away in the Main Game [Nintendo Life]