In the end, Hopton comes down on the side of the 1er Régiment d'Infanterie Légère as well as the 42e Ligne being formed in line.
Hopton debates in text and footnotes the column versus line issue and the historiography. He outlines much of the historiography in fairly complete fashion, though edging toward writing less than fair to a number of authors.
He notes Fortescue's change between his two editions of his work and he includes a discussion of Oman's change of opinion as noted in the second edition - see footnote on page 78 in linked copy below.
Hopton goes into some depth here and and much is usefully presented; others are not. For example his critque of Oman for not explaining "evidence put before me" (the quote given by Hopton): Hopton says Oman "refer opaquely" to the justification when the "evidence shown me by Col James" (as actually written by Oman). Oman's actual note strikes me as a military man pointing out the reality of the evidence to the scholar and the opaqueness is imposed.
This is in a footnote and he allows there that Oman compared this to Bunbury and Boothby. In the main text of his French tactics section, Hopton calls Boothby's account as "scarcely amounts to a positive proof" primarily because Boothby remained behing at the beach and "watched events, at a distance of several miles, from the Bastion di Malta".
This sounds like a strained effort to create controversy that only the author can solve.
In a similar manner, in a footnote, he dismisses the use of the phrase used in Reynier's report of "formés en bataille" (see Reynier's report to Joseph in Mémoires et correspandance politique starting on page 376, with the phrase being on 381) to conclude the units were in line.
I find this an odd deconstructionism since it ignores the normal phrases used for formations, in general, and the descriptions in the remainder of the report, in particular. For example, the use of the phrase "second ligne" to say where the 4e Suisse and the 12 Polish companies formed. This phrase lacks clarity as to formation in contrast to "en bataille".
Later (the footnote reference is before this), in the main text, a broader section of Reynier's report is quoted with the assertion of lack of clarity (from "Le 1ère et 42e régiments, forts . . ." to ". . . en second ligne par échelons derrière le droit du 42e régiment."). Hopton does not allow the French units were in line until he finds other accounts to describe the units (Griois - page 309; see link below. Citing these are useful additions to the story.
In my view they support the original description of Reynier, if read more fully.
Read the entire work and draw your own conclusions on the method.
Yet, the French were in line. - R
Title Mémoires et correspandance politique et militaire du roi Joseph: publiés, annotés et mis en ordre
Authors Joseph Bonaparte, Albert Du Casse
Editor Albert Du Casse
Publisher Perrotin, 1855
Item notes v. 2
Author: Griois, Lubin
Publisher: Paris, Plon
Author: Oman, Charles William Chadwick, Sir, 1860-1946
Subject: Wellington, Arthur Wellesley, Duke of, 1769-1852; Peninsular War, 1807-1814; Great Britain -- History, Military 1807-1814
Publisher: London E. Arnold