One flaw of measuring electrical resistance with a typical multimeter is the low Voltage/Current used in the measurement. You can have a connection with one strand of wire, and it will still show resistance on the bottom end of the meter's resolution - probably tenths of an Ohm. In operation, the higher currents may lead to a significant Voltage drop at this one strand left connection, and possibly failure of that last "hair" from resistive heating.

The resistance measurement doesn't tell you about the ampacity of that connection.

The accelerated corrosion of copper pipe from grounding has been debated at length. With Copper prices causing Gold and Silver to look over their shoulders, PVC seems to be the order of the day for new construction as well as repairs, and the contribution of the plumbing system to the grounding system is going away.

I don't think the connection to the earth beneath our feet is as important as everything being well connected together at a single point so transients become a common mode event. It's great to dump the energy surge into the dirt, but who has data showing how well these different systems accomplish that?