It's not that guy either, or at least he certainly doesn't have the same character model. (Though he certainly seems like a plot thread that was left hanging.)

I've been using the Garland Tools NPC database to check these, by the way. It lists the exact character design settings for each NPC. The "Katana-wielding soldier" is listed in the first unlabeled 'no location' tab (which seems to be for cutscene characters) and anyone else can be looked up by the location(s) where they are found.

(That said, it's not 100% reliable for 'hidden details' or customised character designs, and characters occasionally get redesigned - eg. Estinien-the-dragoon actually has a different face design to how he looks in Stormblood - but it's useful for just comparing character models.)