I do, however it's only the same information as Afterpay themselves release as there is no way of tracking that any other way.
I do try and correlate what I track to Afterpay's reported numbers to try and extrapolate growth between Afterpay updates, with varying levels of success. I was fixated with iOS app ratings and customer number which showed strong correlation until the latest update, so have now taken a more broad based approach where I'm using several estimates to create a range of expectations.
It's not an exact science, but what I track does tend to follow closely along the Afterpay growth story.
I do know member growth has slowed rapidly in AUS, is likely approaching a similar point in NZ, but still has a long way to go in the US (if it follows the same path. Heres the AUS chart: