Apologies for being slightly autistic on numbers. I don’t trust any phone numbers for ratings and reviews, they seem to be switching depending on location, and any place that claims to give an aggregate of them gives different numbers. But then, I don’t understand phones so…
However, Steam has hard numbers linked to actual sales.
Rebirth: 16 090 copies sold on Steam = 353 reviews.
Retribution: 8 957 copies sold on Steam = 303 reviews.
I only have two data points I can trust, but really hard to make a model from them…
Not sure actually, but I do know that the sales might be made elsewhere and then things gets unlocked in the omnibus. For example, Rebirth came out pre-omnibus and has very few direct omnibus sales, but has a lot of omnibus ratings. I assume this is because people got the omnibus entry unlocked later, by asking CoG about it.