No argueing. Grounding/Bonding is an important electrical concept that should be understood. Expecially if troubleshooting issues.
Using the logic of the grounding to the Block as 'confidance' inspiring is miss leading.
If this were true, and there should there be corrision/high resistance at the (-) battery post, your logic implys all will still work well. When in fact things will not. Resistance at either connection will degrade electrical system preformance.
The Engine/Chassis and Battery must be electrically connected (Grounded/Bonded) to one another for proper electrical system function.
