I recall this stat from the SpaceX commentary on their livestream, but my (faulty?) recollection is that the claim was 10% greater payload with hot-staging – is that just another way of saying that it reduces fuel requirements by 10%?
In any case, it looks like they have some work to do on hot-staging sequencing. Maybe not throttle down the 3 core engines so that the booster doesn’t experience negative thrust during the hot-staging separation? It will be interesting to learn what is learned.
Here is a computational fluid dynamics simulation done by TheSpaceEngineer using Blender and based upon accelerations and angular displacements calculated from flight telemetry and video from the SpaceX Webcast of the launch.
If this approximates what happened during the hot staging maneuver, it’s easy to see why fuel starvation of the first stage engines may have occurred and structural failure ensued due to stresses imposed by propellant sloshing.