It does not concern consensus rules, aggregation, or any other integration into Bitcoin - those things are left for other proposals, which can refer to this scheme if desirable. Standardizing the signature scheme is a first step towards that, and as it may be useful in other contexts to have a common Schnorr scheme available, it is its own informational BIP. The encoding of public (and private) keys is unspecified. The R(share) can still be used "online", if share participants publish the R(share), but offline multiparty signing is eliminated in exchange for batch validation. Andrew Poelstra suggests that they should specify that they use the standard encoding from section 2.3 except that they allow only compressed public keys.