Updates to Security and Privacy Considerations section (zcash#45)

This adds some details to the ZIP 226 Security and Privacy
Considerations section to address this
[comment](zcash#680 (comment))

zip-0226.rst

@@ -409,7 +409,9 @@ The details of the changes to these algorithms are in ZIP 227 [#zip-0227-sigdige
 Security and Privacy Considerations
 ===================================
 
-- The notes generated via the ZSA protocol are different from those generated via the Orchard protocol. As with any protocol upgrade, it will be possible to distinguish between notes generated by each protocol. However, all ZEC notes will be fully spendable with the ZSA protocol transaction structure due to the built-in backward compatibility.
+- After the protocol upgrade, the Orchard shielded pool will be shared by the Orchard protocol and the Orchard-ZSA protocol.
+- Deploying the Orchard-ZSA protocol does not necessitate disabling the Orchard protocol. Both can co-exist and be addressed via different transaction versions (V5 for Orchard and V6 for Orchard-ZSA). Due to this, Orchard note commitments can be distinguished from Orchard-ZSA note commitments. This holds whether or not the two protocols are active simultaneously.
+- Orchard-ZSA note commitments for the native asset (ZEC) are indistinguishable from Orchard-ZSA note commitments for non-native Assets.
 - When including new Assets we would like to maintain the amount and identifiers of Assets private, which is achieved with the design.
 - We prevent a potential malleability attack on the Asset Identifier by ensuring the output notes receive an Asset Base that exists on the global state.