https://support.apple.com/kb/PH13572?locale=en_US . talks about how you can "tick off checkboxes" to filter out MIDI messages such as sustain, etc. This is how I remember older versions of MS being, even MS3. Now, however, there must've been some update; it seems the UI of the MIDI input tab of the Channel Strip Inspector has changed. Now it's clunkier…I have to go to the add the input controller (e.g. 64 Sustain) and then select filter. Not impossible to do, just less intuitive than the old design where you just ticked a box to filter out Sustain or whatever. The online manual (that link was updated just a month ago!?) should reflect that change, since it's been like this for at least a year.