So, "written mention of Odin" seems to mean written as "Odin', and not as "Mercury".
It also mentions some debate over if the Goths actually worshiped Odin/Mercury, but I am too ill-informed to make sense if that's relevant.
I did manage to find a scholarly reference to the topic at https://helda.helsinki.fi/server/api/core/bitstreams/c11e69e... ("Pre-print papers of THE 18TH INTERNATIONAL SAGA CONFERENCE SAGAS AND THE CIRCUM-BALTIC ARENA. Helsinki and Tallinn, 7th–14th August 2022")
> The problem of Mercury
> Despite lack of Germanic evidence for the existence of a cult of Wodan/Óðinn before the fifth (or perhaps even the sixth) century, as presented above, many scholars maintain ancient roots. For example, disregarding critical scholarship on various individual sources, Schjødt reiterated that “taken together, they strongly indicate that Óðinn, although not exactly the same as the god that we know from the Nordic sources, has roots reaching far back in time, probably as early as the Indo-European era (at least 3000 BC)” (Schjødt 2019: 67). ...
> The reading of interpretation romana maintains that Tacitus’ famous description of Germanic deities, Deorum maxime Mercurium colunt, should be understood to signify Wodan/Óðinn. Of course, it has already been shown by Karl Helm that this was a historical trope copied from Herodotus, and/or Caesar’s Commentarii de bello gallico (Helm 1946: 7-12). The fact that Caesar was talking about Celts, and his description of religion among the Germani mentions worship of the sun, moon, and fire, does nothing to secure the reliability of such ‘historical’ sources. Either way, the argument that the foremost deity interpreted by Tacitus as a ‘Mercury-type’ must be Wodan/Óðinn is a projection of the latter’s supremacy in Old Norse material onto a Germanic society several centuries older. This becomes a circular argument and cannot be leading.