You are correct Endless. I still think it would be nice if it was universal - would combine the isbuttoninfo, remotekeypressed, islistiteminfo, and however many others I forgot.
Maybe it's not as big a problem as I thought it was - but I still get hung up on the "SetMessagePort" and "SetPort" compatibility issue too.
In the 3.1 firmware which runs on legacy Roku devices, the SetMessagePort method is not supported on the roScreen and roUrlTransfer components. For compatibility with these devices, your channels should call SetPort on these components instead.
Maybe a future firmware update will add both methods for 3.1 firmware (which would be 3.2 firmware, HA)