As this ride was in Australia and assuming the bike is legal [1], the actual limit is 200 or 250 watts (depends on the state) and must cut-out at 25 km/h (not that last criteria is likely to apply on the Canning Stock Route). So nothing more than e-assist.

He was actually quite slow on the ride as well so not sure he really even benefited from having the e-bike.

[1] It is an off the shelf bike so I would assume it was legal