He was certainly going some on the dashcam clip on you tube. Maybe as a result of the increased RPM that is detailed in the report, which was not usual compared to other video clips of previous flights by the pilot.
Thought that aeros would generate more than 3G, and an earlier display was 5.5G and we have no idea if the aircraft had exceeded limits prior to Shoreham, causing an issue that went undetected. As there is no data on the fatigue meter readings taken at the last annual inspection and during the investigation.
Another AAIB report G-HHUN makes interesting reading with regard to engine surges and stagnation that can occur. Could this explain the unusual behaviour of the RPM detailed in the report for BXFI.