I am re-posting this because I incorrectly stated the problem in my earlier submission.
Sometimes, especially after a phone call, Siri's voice changes to the earpiece from the speaker making it difficult to hear if you are away from the iPhone. This routing persists even after re-starting VoiceOver. It seems to revert back to going through the speaker after some time. Alternatively, re-starting the phone will fix the problem.
I am using an iPhone 12 running IOS 15.2. I have spoken to somebody else, who uses an iPhone 11, and he is having the same issue.
Has anyone else experienced this? I will report this to Apple accessibility.
Thanks for any feedback.