My guess is that they know it started in two places. If they had even 40 minutes in the building while it was on fire, I think they’d have a fairly decent sense of this.
If it did start in two places, it would take more belief than I can muster to hold that it was not intentional. One might not have absolute certainty, but one would have moral certainty, which is sufficient to act upon.
Could be. The fire starting in two places would pretty much clinch it. On the other hand, I could imagine a fire seeming to start in two places but not actually doing so. Like if it started in one place and then were quickly channeled internally to another spot where it flared up. To me there’s not enough info to draw solid conclusions yet.