Current ABCI++ specification, as of tendermint/spec#366, includes the whole block header in Request* calls to PrepareProposal, ProcessProposal, and FinalizeBlock; in the same way as ABCI included the header in RequestBeginBlock.

It is unclear whether the whole block needs to be exposed in these calls. We have agreed on making the implementation progress and, when implementation of Request* calls to PrepareProposal, ProcessProposal, and FinalizeBlock are clear, we will make a decision on the header parameter. This will be how we handle this issue.