These vital records lists can be found in the local German newspapers going back to 1872 for births and deaths, but even earlier for marriages. What these lists reflect is only what was _recorded_ for the day that the newspaper collected the information, sometimes multiple days worth. The information changes in different eras, and for various periods the information changes: marriages identified by marriage licenses, not registrations; and burial permits, not deaths.
For researchers, the problem has always been when was the birth, death or marriage reported and then recorded? There are examples of families reporting early births retroactively (my Oppermann ancestor reported his daughter's births in Manitowoc Co. in the 1860s, in 1872 - these are found in the state registry). That's why "recording date" is important to take note of for any early vital record. One Wisconsin archive found a snafu that was created in their index when the recording date was confused with birth date.
Much later on, late birth registrations are collected separately as "Delayed Birth Records" and most of that collection comes from those records reconstructed for Social Security registration: 2 of my grandparents used insurance policies, baptism records and family depositions/affidavits to report their own births from 1888 and 1893.
The newspapers weren't producing original reporting in these vital records lists. But it's possible that a birth, marriage or death that didn't make it into the local Register of Deeds OR state offices may be found in a random clipping or celebratory notice found in newspapers and indexed in "Milwaukee's German Newspapers; an index of death notices and related items" (1844-1950).email@example.com
, originator/compiler/editor, Milwaukee Wis.
Indexing Milwaukee's German newspapers continuously since 2007... helping family researchers find their ancestors among Milwaukee's 99%.