Do they need to post sources for every possible municipality? Los Angeles is actually a very definitive source on them being bad for sanitation systems. LA is a pretty young city, they really don't have any terribly ancient sewage systems. There were apparently still wooden pipes in service in Philly in 2017 [0], probably there still are some in service right now. LA's oldest infrastructure could conceivably be from the 1860s, and realistically their oldest infrastructure would be from the 1910s. If their sanitation district advises against it, why would we expect older cities like NYC or Baltimore to fare better?

[0] https://philly.curbed.com/2017/5/5/15545532/philadelphia-wat...