I assume you are looking at the first search result which is the wiki page?

To be fair wiki attributes the first NATIONAL observance to 1868 and Commander in Chief of the Grand Army of the Republic, John A. Logan.

It then goes on to say:

This national observance followed many local observances which were inaugurated between the end of the Civil War and Logan's declaration. Many cities and people have claimed to be the first to observe it. However, the National Cemetery Administration, a division of the Department of Veterans Affairs, credits Mary Ann Williams with originating the "idea of strewing the graves of Civil War soldiers—Union and Confederate" with flowers.[7]

So while they dont credit 1866 and the freed SC blacks it does make note that it wasnt created by Logan out of the blue.

Ill finish by adding what I said to the op, "Im no friend of Google but this post is all kinds of fucked up. We dont need bullshit like this to make our case."

Edit to add some follow up research on Mary Ann Williams:

Mary Ann Williams, the secretary of the Ladies Memorial Association founded in Columbus during the winter of 1866, wrote a letter that was published in March and April of that year in more than two dozen newspapers across the country. The letter reported on the association’s resolution, one year after the end of the Civil War, to “beg the assistance of the Press and the Ladies throughout the South to aid us in our effort to set apart a certain day to be observed from the Potomac to the Rio Grande and be handed down through time a religious custom of the country to wreathe the graves of our martyred dead with flowers.”

For further reading:

https://www.ledger-enquirer.com/news/local/article80609312.html