Well you won't get around it.
The Little Phatty has some funky MIDI implementation based on the fact it wasn't designed with the thought of being a Master Controller.
What you are experiencing is that even with the Local set to Off the Phatty still sends and recieves MIDI CC messages, it only serves to seperate the controls from the sound engine.
With typical synths Local off along with Poly mode allows different parts to respond to different MIDI channels on, while Omni makes it respond to data on any incoming channel.
Since the Phatty was a mono synth they designed it so that using different Send and receive channels would mean the unit wouldn't see sound from the keys unless it was being rechannels to that channel.
So if the unit was sending on channel 1 and receiving on channel 2, the MPC would need to rechannel the MIDI data to channel 2 for the Phatty to play sounds.
The other solution on some synths was a setting that allowed you to determine if the MIDI out acted as a MIDI thru.
The Phatty's MIDI chart shows that it wasn't designed with a MIDI controller job in mind.
Since it uses MIDI CC to control it's own sound engine as well as sends/receives it without the ability to ignore or filter it's can be a problem.
As I said earlier
the maker wrote:I wouldn't really trust Moog's MIDI implementation , but that's a whole different story.
Based on the availble options on the Phatty, if you have the Send set to one channel and the Receive set to a different channel with the Local off, the MPC sequencer would have to rechannel the incoming to the correct out channel to play the Phatty.
Can't really check since the Phatty I had was a just for a Demo.
Fix coming in new OS update.