ipip-412: note why we kept separate parameters

#412 (comment)

src/ipips/ipip-0412.md

@@ -159,6 +159,19 @@ Several alternative approaches were considered before arriving at the proposed s
    saves a few bytes in each round-trip. Also, :cite[rfc6648] advises against
    use of `X-` and similar constructs in new protocols.
 
+4. The decision to not implement a single preset pack with predefined behavior,
+   instead of separate parameters for order and duplicates (dups), was driven
+   by considerations of ambiguity and potential future problems when adding
+   more determinism to responses. For instance, if we were to include a new
+   behavior like `foo=y|n` alongside an existing preset like `pack=orderdfs+dupsy`,
+   it would either necessitate the addition of a separate parameter or impose
+   the adoption of a new version of every preset (e.g., `orderdfs-dupsy+fooy` and
+   `orderdfs+dupsy+foon`). Maintaining and deploying such changes across a
+   decentralized ecosystem, where gateways may operate on different software,
+   becomes more complex. In contrast, utilizing separate parameters for each
+   behavior enables easier maintenance and deployment in a decentralized
+   ecosystem with varying gateway software.
+
 The proposed solution of negotiating the block order through headers is
 future-proof, allows for flexibility, interoperability, and customization while
 maintaining compatibility with existing implementations.