Why might revenue in the Asset report not match revenue in the Video report?

This might occur when assets and the videos they claim have different monetization policies enabled.
This happens when a video contains multiple assets. Revenue from all assets should add up to video’s revenue.
This only happens with music, if ownership is split between performance and composition assets.
This can happen when an asset has multiple owners in different territories: revenue can vary from country to country.

The correct answer is:

This happens when a video contains multiple assets. Revenue from all assets should add up to video’s revenue.