you wrote;
The weights have to "drop" faster than gravity in order to impact the wheel - and make it rotate! - at those rpm's.
Do you still think it was a gravity wheel?
Here I think your thinking is wrong.
Let me explain how i see it.
Depending on the wheel size you can calculate the maximal speed of a weight in free fall. H=1/2 * g *t *t
so with a diameter of 3,40 m we can calculate the speed of the weight hitting the rim.
This will be the maximal speed, in reality you can not reach
the 3,40 Meters, because you must have an internal construction.
now the if: if you have the speed of the weight and mass which is hitting the rim at about 8 o'clock then you can transfer some energy to the standing rim.
Here I say standing rim, because the wheel standstill at the beginning.
You have a speed difference, rim to falling weight, which you can make use of. Rim speed = zero, weight speed = ?
When the Rim begins to turn, speed > zero, weight speed still ?
the wheel will run at constant speed if the difference Rim to falling weight is nearly the same.
To answer your questien, Yes it is a gravity wheel.