Though it can be used two-handed (versatile weapon trait) in D&D 5e, as the longsword in real life, it is a bit too big in the picture. It looks a lot like the claymore swords as seen in the movie Braveheart.
Wikipedia says :
"The Scottish name 'claymore' (Scottish Gaelic: claidheamh mór, lit. 'large/great sword') can refer to either the longsword with a distinctive two-handed grip, or the basket-hilted sword developing from a rapier. The two handed claymore is an early Scottish version of a greatsword."
So the claymore is considered in between a longsword and a greatsword, which I am pretty sure is what is in this picture.
AFAIK a typical claymore is a hand-and-a-half sword. I have a couple of examples of the same general type next to me, they're about 3" or so longer than a typical arming sword and maybe as much as 6" longer than e.g. a Viking sword.
I have no "hands-on" experience of D&D prior to BG3 but I am aware that older nomenclature and statistics tended to be extremely problematic; and that things have improved a lot more recently. Regarding the above picture, it's "a bit big" but not so much that I find it enormously bothersome, except that it's slightly the wrong style for the size and general era. But it's not terrible.
Maybe my expectations for RPGs in general are low but it's just nice to see a sword that isn't
covered in a million pointy bits that will cause more injury to the person holding it; and which isn't made with a weirdly thick blade that supposedly weighs 10× more than the real thing...