Original Diameter of Ancient Impact Craters
There is a recent paper(open access) that i assume the news item refers to. That paper does not  mention 430m. They use a magnetic anomaly to extrapolate the original crater size from the eroded central uplift. The crater itself is long since eroded.


  Therefore, the ~20 km diameter magnetic anomaly has been interpreted to represent the remnant of the deeply buried central uplift of the structure, which is consistent with an original crater diameter of 70 km


and


  The present day exposure represents a deep erosional level, as neither impact breccias nor topographic expressions of the over-turned rim or central uplift are preserved.


The samples for age determination were taken from a structure called "Barlangi rock":


  The structure is centred on a large exposure of granophyre known locally as Barlangi Rock (Fig. 1; 118˚50′E, 27˚10′S). Barlangi granophyre is a sodic rhyolite[...] that has been interpreted as an impact-generated melt rock[...], radiating dyke-like apophyses of granophyre outcrop as far as 3 km from the centre of the structure


This is not the central uplift itself like from a crustal rebound, but


  ... has thus been interpreted to have intruded into the Yarrabubba monzogranite along faults rather than forming a flat-lying, crater-filling melt sheet ...


The filling at Barlangi has a complex age range (2.79 to 2.23Gy). 2.229 has been determined out of this as the most likely date of the impact. And of course, since then it has been exposed to weathering and erosion.

So there are two separate things here: the size inferred from magnetism, and the age determination from an intrusive melt.

Wikipedia estimates the Manicouagan structure's original diameter to ~100km. More on that event and it's proposed impact on the environment can be found here (open access). The introduction names an initial diameter of 90km for Manicouagan.

Hope that clarifies. Corrections and annotations welcome.