TLL is SMB 2 and it uses levels and assets that were developed alongside SMB 1, but then they were *gasp* not included in the game and you had to buy them later when TLL came out! That means SMB 1 cut content that was good enough to release and made you buy it separately. Damn Nintendo, always out to pillage your wallet at every opportunity.
Prove that the shop items for Diablo 4 weren't at one point assets to be included in the base game that were then edited out or otherwise cut before release. You can't, because no one but the developer teams know what got kept and what got scrapped.
If it was cut it's not part of the game anymore. It's extra, and you can pay extra for it. Just like you can field your Space Marine army with generic iconography out of the box or you can pay extra to get their particular chapter badge decal sheet.