Glad you brought that up. I am now under the impression that it will be a rolling launch. Both Thunderbird and Pipeline have a set of drive tires right before the LSM motors begin on the track, and both of those stop for a few seconds before launching. Penguin Trek, however, does not have a set of tires immediately before the LSMs, and is a rolling launch. Caldera is the same, as it's only LSMs after it departs the station.
Now that's not to say that it
couldn't stop there without a set of tires, as the LSMs would be entirely capable of controlling the train at that point (especially because that first launch section is its own valley). It's not written-in-stone evidence, but just comparing B&M's existing LSM rides, I think it's a plausible 'tell' that it's a rolling launch. And like you said, it'd be a neat homage to Volcano, especially if the back car is still slightly on the curve when the train starts launching