Google Chrome 72.0.3593.0 (Official Build) dev (64-bit)
Google_Caroline.7820.384.0
and 
Google Chrome	71.0.3572.0 (Official Build) dev (64-bit), Google_Caroline.7820.384.0 

Steps to repro:
# Enable Select-To-Speak via Settings > Manage Accessibility Settings
# Set your system voice to be the same as your STS selected voice. That is, for example, make sure that Chrome OS US English is set both in Settings > Manage Accessibility Settings > Text-to-speech voice settings > Preferred Voices and in the STS extensions settings page: chrome-extension://klbcgckkldhdhonijdbnhhaiedfkllef/options.html

# Prepare another voice for English, I did this by installing the "Willoldman" US English Acapela voice via the extension chrome-extension://hfpbgbaepoblbkbmpojjnpkeikgoadil/shell.html 

# Go to the TTS settings page (not the STS settings page) and change the Preferred English voice to be the Acapela voice installed for English.

Expected: STS changes its voice based on the change in the STS page
Actual: continues speaking in former English voice (the default one)

# Go back to the STS Settings page and refresh the page
Expected: voice is now set to Acapela voice per the TTS setting 
Actual: voice still listed as the default Chrome OS US English 


Note that this does NOT repro with ChromeVox, ChromeVox switches voices as soon as you change the TTS settings page. The ChromeVox setting page is also automatically updated with the name of the Acapela voice.