Wihtout questioning your quote of Oman, the 1913 version I linked in yesterday has a slightly different - yet clear "prove" - text, rather than "seems to prove" in the version you quote. So, I the link is to page 78 and the footnote reads:
"* Till lately I had supposed that Reynier had at least his left wing, or striking Echelon, in columns of battalions, but evidence shown me by Col. James proves that, despite of the fact that the French narratives do not show it, the majority at least of Reynier 's men were deployed. This is borne out by Bunbury's narrative, p. 244, where it is definitely stated, as well as by Boothby's, p. 78."
Interesting that both are 1913 sources, although the link has "second impression" on the title page, so it would be important to confirm that the shift between "evidence put before seems to prove" and "evidence shown me by Col. James proves" was the correct order.
If it is the reverse this would show Oman backtracking.
I say this because in 1929, Oman issued Studies in the Napoleonic Wars, wherein he includes "The Battle of Maida" nad he presents the 1ère Légère and 42e Ligne in column (pages 52 and 53) whereupon he includes his "fairest fight between column and line" comment on page 53.
A strange lapse or change of mind in light of "evidence . . . proves" in the footnote in the version linked below.
In contrast to Oman, Arnold remains consistent in his view. - R