Despite the talk page correctly pointing out the name is a misnomer, for some reason the Wikipedia page as a whole hasn't been corrected. Check this article and discussion out to get an in-depth breakdown of how people have gotten so thoroughly confused:
Or a TL;DR if you can't be bothered reading all that:
1 - the one Greek/Roman reference we have linking the word "rhomphaia" with the Thracians, Plutarch, describes it as a
straight weapon. "Rhomphaia" in Greek simply referred to pretty much any heavy edged metal weapon - including swords or, at a stretch, axes. So the Thracian rhomphaia would not be curved.
2 - Further investigation shows that the tribe depicted on Trajan's monuments using two handed choppers are probably Bastarnae, a different tribe to Thracians. So even if the rhomphaia described as Thracian by Plutarch was curved (which it wasn't by his own words), that image of a two-handed chopper wouldn't have any strong link to the word "rhomphaia", though it could possibly be called a falx.
3 - While this requires assumptions being made, it is possible that the two-handed chopper depicted as held by the Bastarnae was not even a dedicated weapon. It could instead be an agricultural tool taken up for self-defence against a Roman massacre, evidenced by the fact that women and children and wagons are present in the scenes where the two-handed chopper is used. Similar two-handed chopping tools are used to this day in agriculture.
In summary, the long hockey stick as shown in Bannerlord is totally wrong (as you know), the name "rhomphaia" used to describe a curved two handed chopper is almost certainly wrong, there is also no evidence for the Thracian culture using any sort of curved two handed chopper under any name, and it is potentially questionable whether the two handed falx was even a dedicated weapon at all.