I'm afraid that there are more problems with Cabbage's handling of aftertouch on OSX.
@alcomposer drew this to my attention with this demonstration:
Cabbage output on the left, MIDI Monitor in the middle and Terminal Csound on the right.
I did my own test here:
This time comparing between Cabbage and MIDI monitor while I play two long notes with crescendo-diminuendo of aftertouch on each note.
I've attached a MIDI file of two similar long notes here:
AftertouchTwoLongNotes.mid.zip (1.3 KB)
You can play this into Cabbage from Reaper via the IAC MIDI device as I have done in this video.
Cabbage is on the bottom left, Csound top-right.
Just a simple bit of Csound code will print this: