To the best of my knowledge these studies are rather controversial: they may be false positives, and there isn't enough corroborating evidence. It's certainly a possibility – I don't expect we'll ever establish the exact timeline of the spread for sure.
The wastewater study in Italy is pretty good and fits the pandemic timeline and doesn't claim anything particularly outrageous. They had lots of samples turn positive, the ones that turned positive generally stayed positive. It was just a bit more than 2 months before the first recognized deaths, which fits the timeline of a few weeks of cryptic spread, 4 weeks of doubling every 3 days to get to >1k infected, followed by 3 weeks for the disease to progress to death.
Now take the traveling of people working in (fast) fashion, and where those clusters are into account.
The first Italian wastewater study took samples between February and April.
While the timeline of the 'dramatic actions' article suggests intervention and meddling with data by politicians by at least early December.
The first documented COVID hospitalization was 16 Dec 2019. The first sample was sent for sequencing on 24 or 25 Dec 2019. 27 Dec 2019 was the date of the first medical report.
It was between those days an 20 Jan 2020 when Zhong Nanshan went public with the information that it was communicable human-to-human that the government in Wuhan was dithering. Long after the virus was already in those samples in Italy.
