Detached garage - metallic path back to house

Older detached garage with 3 wire feed and wired like a regular panel (grounds/neutrals bonded/connected). There was a abandoned copper water line that was fed from the house. Question: I know this water line is a metallic path, but this is what’s confusing me (copied from an old thread):

There are no continuous metallic paths bonded to the
grounding system in each building or structure involved.

I’m assuming the water line would need to be bonded to the grounding system in order for this to require a 4-wire feed and ground/neutral separation, no? So the presence of the water line doesn’t mean anything, in the case, since it’s not bonded to the grounding system? Generally speaking, I don’t think I’ve ever seen anything bonded to the grounding system at a detached garage/structure (e.g. water, phone, cable, etc).

Let’s assume that it’s not abandoned so then it would qualify as a continuous metallic path between the two structures. A metal piping system in the detached garage is required to be bonded to the electrical system so with a 3-wire feeder that bonded metal water pipe would be carrying part of the neutral current back to the house.

You said that the pipe is abandoned does that mean that it has been cut off somewhere? If so then the 3-wire feeder would have been acceptable for an installation under the NEC prior to the 2008 code cycle. As I’m sure that you know this panel looks like it was wired by a preschooler with several other issues that need to be remedied.

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Thank you.