As the user in THIS thread found out, Logos is not utilizing the various system voices on macOS. To reproduce, I tried the "read aloud" feature using the NIV. It played the voice I was accustomed to ("Alex" in macOS). I changed my system voice to "Siri Female (US)" but Logos still used "Alex." I then deleted "Alex," restarted Logos AND my Mac... but Logos still uses "Alex."
FWIW - I am using the M1 MacBook Air. With the iOS mobile app running on my Mac (very cool, btw), it DOES use the Siri voice.