Synth inserted as FX - transport needs to be running to receive audio from another synth

Granted, this is one of the more complex setups, but pointed out an unexpected behavior for me. I am doing a demo of Stutter Edit, with the generic setup as follows: Geist inserted with all stereo output tracks visible. One instance of Stutter Edit inserted on a single sub output of Geist.
 
Stutter Edit is an Audio FX that needs to be configured as a synth (to allow for MIDI input, which is required to drive the FX chain).
 
Noted oddity: Unless the transport is actually running (either by shutting off "Stop at Project End" or having other track data present), Stutter Edit is not being passed audio. Since Geist is its own engine, any pure Audio FX in that same bin is fine with the transport stopped (i.e. straight-up audio FX see the audio data).
 
Nothing to resolve here, really. More an observation.
 
Edited to clarify behavior observed.