IT should be the other way around. IF the metal piping were continuous, then it also was contiguous with the metal pipe in the ground which provided the ground/bond. WHEN there was NOT a metal underground line, here the electrical panel had to be labeled "Non-metallic water service pipe", so everyone knew NOT to rely on the water piping for grounding. ANY partial sections of metal pipe COULD be energized, so they SHOULD be bonded.
There is absolutely no reason to bond a short piece of metal water pipe under a house. Just what is likely to energize that pipe? Unless there is something wired to that pipe such as a water heater then there is nothing that is likely to energize it. If the water heater did somehow energize the water heater then the equipment grounding conductor that is installed with the branch circuit will carry any fault current back to the service.
When connecting a system to earth using such items as ground rods or metal water pipe the only reasons this connection is made is as follows;
250.4 General Requirements for Grounding and Bonding.
The following general requirements identify what grounding and bonding of electrical systems are required to accomplish. The prescriptive methods contained in Article 250 shall be followed to comply with the performance requirements of this section.
(A) Grounded Systems.
(1) Electrical System Grounding. Electrical systems that are grounded shall be connected to earth in a manner that will limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines and that will stabilize the voltage to earth during normal operation.
When a metal water pipe is in contact with earth it is the grounding electrode conductor that does the bonding of the metal water pipe not the fact that it is connected to earth.