You know what's way more neutral than "vehicle fault"? Something like, "We cannot narrow the cause yet, as the investigation is too young."
The latter eliminates (at least for now) driver error and intentional causes, but not manufacturer defect. Indeed, as soon as one hears "vehicle fault", ones attention is drawn to the possibility of manufacturer error (rightly or wrongly). This is particularly true if the manufacturer has had recalls and such in recent years. If I'm not mistaken, some people have discussed Land Rover's issues with manufacturer defects in recent years. In fact, I think you've mentioned it when propping up your motive for this scandalous misdirection by the fire brigade.
These lawyers and others who restrict what the chief[1] can say really dropped the ball here. They directed him to announce the arrest of the driver to distract attention away from Land Rover, but they failed to censor his attribution of vehicle fault when he could have simply remained silent.
[1]
Truth be told, I'm not positive whether it was the chief who made the announcement of vehicle error and the arrest or some other official on Oct. 23, but my point will stand regardless. It appears that the discussion of both the arrest and cause of the fire come from a police statement or conference -- not sure which.