There were a bunch of posts about this problem in one of the prerelease threads (I can't seem to find it right now). The summary is that the previous Reaper behavior with EZ Player was absolutely, unequivocally, a bug. That plugin specifically does not pass through input MIDI s part of its design (don't ask me why). Because of a Reaper bug, the input MIDI would get merged with the plugin output MIDI, and this exact same bug caused occasional hanging MIDI notes in this and other plugins. So we fixed the Reaper bug (that happened to make using EZ Player, but no other plugins that I know of, more convenient in Reaper), but added this new MIDI mode so that people who wanted the old behavior with EZ Player could still get it.