There is not actually any mythology here, just a reasonably purported misconception.
Myth and mythology are not the same thing. Example contrast: Mythbusters vs. Mythologybusters.
This is a weird article. Trying to definitively describe what millions of people did over 100’s of years with a binary “yes they preferred beer because water was unsafe” or no they didn’t seems like it would take hundreds if not 1000s of pages. Even the 14th century monk example saying they preferred water comes off as an exception that proves the rule type example. I’m not saying they’re wrong, but I guess I never thought that “medieval people preferred beer” myth meant all the people all the time either. Then they go on to seem to ridicule anyone who disagrees with them.