Thanks for asking, I love this stuff.

"you seem to consider blues at least as many pieces of evidence in the Delta from around the exact same time..." The Delta has Alec Lee in roughly 1902 and the Tutwiler guitarist in about 1904. Cleveland (MS) was "some time between 1905 and 1910" per a 1924 article based on an interview with Handy. Unfortunately we don't know what Handy heard in Cleveland, which might well have been the non-blues "don't allow" section of "Memphis Blues," given that an unpublished manuscript by Handy mentions, "McCoy [the guy whose band he heard in Cleveland] used to play a piece called: 'I’m A Winding Ball And I Don’t Deny My Name,'" a related song to the "don't allow" song. Charles Peabody was 1901-1902 and we don't know whether the lyric with "murder" in it he quoted without music was in a blues or not, since many lines were used in both non-blues and blues songs. And I think that's it for evidence of blues in the Delta before 1912, two solid and two maybes.

No, I don't somehow "prefer" the Louisiana examples to earlier examples such as "Got No More Home Than A Dog" in Indiana before 1900. But for the 1900-1909 period, for what's that worth (and the Delta has none from the 1890s) I count three solid Louisiana, two solid Delta.