Are SYNC BRIGHTNESS seting in series?

SYNC master (esp32) is sending brightness and 2 slaves (esp8266) are receiving brightness. From the PHONE WELD app, the main page that shows all devices on one screen, The Master can only send brightness to the 2 slaves if the slaves have some brightness already defined (say 1/4 or total slider) It appears just like a sound mixer that has input volume levels set to 0, so the master volume doesn’t do anything. I thought SYNC sending and receiving brightness would override my slaves individual brightness settings. Am I wrong?