We must also remember that it is possible that some of the early sources quoted in the article misunderstood "point blank".
LD
More likely, the "definition" has evolved over the centuries.
Captain George Smith's 1779 Dictionary: "Common experience, together with some of the greatest artists in fortification, unanimously agree" on the distance."
"Even the French held the same view of musket capabilities."
Not to argue apples (smoothbores) and oranges (rifles), or go
ff on ctg guns, but, if you are familiar with the "Plevna Delay", the Ottoman Turks used Peabody-Martini .45 caliber rifles to badly damage the Russian forces with plunging fire at (a premeasured) 2000 yards! (When the range closed, the Turks switched to 1866 Winchesters, and annihilated them.)
Brown Bess volley fire at 300 yards, "when attention is paid to the loading" and trajectory, would likewise have a worthwhile effect.