This is true!
I found excessive corrosion in my Pro1 headed SBC when I tore into it for my current rebuild.
It only had 1 ground from the battery neg terminal to the block, that's it!
I don't think you can have too many grounds.
Do what you want but I WILL BE installing a ground from my battery negative terminal to the frame, another ground from that point to the engine block, each head will get a cable to the frame, and there will be a smaller ground wire (8 gauge) to the body.
Also, some of the import crowd replaces stock ground wires with larger cables to help reduce resistance. They "claim" Hp increases with this. Take it for what it's worth.
1 last thing....use good cable / wire with properly installed ends / connectors !! Not that real rigid crap with about 10 strands !!