It was like 2017ish.
It was a bit of a Frankenstein "model". We really wanted some sort of probabilistic convective scale guidance, but it takes a lot of computing to run a large CAM ensemble. So somebody smarter than me decided to take what we already had running (ARW, HRRR, NSSL, etc) and turn them into a poor man's ensemble along with the 12 hour old versions of the same models.
Pros: it provides some probability-like forecast parameters, it has a range of models/convective cores that can provide insight when biases are known.
Cons: it is not a true ensemble, as you would prefer one core and the entire range of possibilities for that.