The proposal suggests that output descriptors should explicitly define entropy with the unspend() function, ensuring clarity and precision in the description of how outputs can be spent. This explicit definition aligns with the first three properties outlined for output descriptors, emphasizing predictability and determinism in their structure.

In contrast, wallet policies might omit the direct specification of entropy, given the overarching standard would necessitate that the content of unspend() is inherently deterministic and can be inferred from the remaining parts of the descriptor. Here, the fourth property comes into play, specific to wallet policies. This additional property underlines the significance of a deterministic process in generating wallet policies, which would not require the explicit expression of entropy as part of their composition.

Thus, by separating the properties of output descriptors and wallet policies, we acknowledge and cater to their unique requirements. Output descriptors are designed to be explicit and detailed, while wallet policies rely on an implicit, deterministic framework, which simplifies their structure without compromising functionality. Each serves its purpose with a tailored set of properties, ensuring both clarity in transaction processes and efficiency in policy generation.