Anonymous Fictional Characters and Dates

Factual Questions
1

I have read certain fiction books that blank out parts of dates or peoples names for no apparent reason.

For example, the author might write: “It all started in 194-” or “We were at the house of Monsieur M-.”

Does anyone know the reason for this?
Anonymity doesn’t make sense because the books (and presumably the dates and names of people) are fiction.

2

It’s a literary conceit. But giving sort of a name, it makes the story seem more real, as though the name was just changed to protect the innocent. The practice is pretty much in disuse nowadays, except for stories that are striving for an “old” effect.