I would love to find more information on this. It's really hard to judge how the ride is performing while Disney continues using these boarding groups because they completely hide the number of people actually getting to ride. On the surface the ride looks like it's doing pretty well, but who knows. To see the boarding groups reaching capacity basically everyday before 8am is a bit suspicious, unless capacity has been fairly limited.
The most seemingly reliable number I've seen was that the ride is currently being operated at about 60% capacity. If we assume the ride is designed to be in the 1800-1900/hour range, then that puts us at ~1000/hour currently.
Another thing to consider is that we're assuming that the boarding group mechanics are consistent from day to day, but Disney could easily be changing the number of people per group. Perhaps they've reduced capacity in the primary groups, while implementing these "backup groups" at night to take some pressure off themselves? Or maybe they are feeling more confident and the ride is getting more consistent.