And there is little reason to believe that ethanol producing bacteria have a selective advantage. Why would they be maintained in someone's mouth microbiome?

My worries are with translocation of oral bacteria.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6427756/

Once it is in the gut you have Small intestinal bacterial overgrowth (SIBO) issues. (could have ;)

https://www.youtube.com/watch?v=wMWy2Rg6Ul4