Taking your post at face value, I would say we know it’s twice as infectious due to more testing and/or better data. So we know that more people have been infected.
We didn’t discover a bunch of dead people that were infected. So the denominator increased relative to the numerator.
The authors of this study are almost certainly not the only ones who "knew" it was twice as infectious based only on the data available back in early February, before anyone outside of China was testing at all.
We didn’t discover a bunch of dead people that were infected. So the denominator increased relative to the numerator.
Not stating this as fact.