No body = reasonable doubt.
Absolutely not true. Not even close.
And the whole argument isn't about the law, it's about the mindset that establishes a dual standard that excuses all kind of horrible actions by people riding in cars.
False.
You started this whole subthread by saying "yet when "vehicular" gets thrown in it carries a much less consequence, so killers who use a car get a pass. " and that was in regard to the legal consequences of killing somebody.
You may believe in that "mindset", but the facts say otherwise, and it has bveen getting more so with the introduction of more severe penalties, and new offences such as causing death by careless driving. Which is a situation where you would NOT get charged with manslaughter - mere carelessness is not enough for that, it has to be gross negligence - which would result in "causing death by dangerous driving" if it were in a car.
I would agree that the situation 20 years ago was largely as you suggest, motorists were treated far more leniently than those causing death in other ways. But it is just not true any more.