Why is the DLC not allowed.

I understand for the normal version everyone might not have access to the DLC but the complete collection comes with all of the DLC. The NX Digimon and the Sistermon's

I am just trying to understand the reasoning for the ban on the DLC from the complete edition of the game. Thank you

Going by definition: DLC, or downloadable content, refers to additional content gamers download for video games after their initial release.

Therefore DLC is generally not considered as part of any game for speedrunning. Even if the community were to decide to want to run with using the DLC, it would become its own category as it usually just breaks the balancing of the game similar to NG+ runs.