Guy reported the observation to Spectrasonics and I'm happy to say that 2.4.2c, hot off the presses (released today), fixes the issue!
Whereas before on my 8700k with the Cream of Emotion 1 patch I was barely able to make it to 7 notes before hitting the CPU wall, with this new version, after cranking polyphony to 64 voices, I'm able to simultaneously play all 64 voices with room to spare (about 70% of a core).
The full changelog:
Includes the following features and fixes:
• Fixes issue where Granular would not work correctly in some scenarios (primarily on Windows)
• Fixes issue where some soundsources would not load properly