At home I have a 1:1 ratio. I've got my own well and my own pump, so every liter of water I get out of the well flows out through my tap. I guess you could argue that the electricity needed to work the pump may be produced by means that waste water.
In the vegan world its standard to count every drop of rain that hit the livestock pasture as being used, therefore its fair to count the rain that ran off the factory roof where the pump was manufactured as used.
Wells don't dig themselves and although that doesn't happen often, it does take a lot of water to do it, and make the gear to do it, and get the diesel fuel out of the ground and onsite to run the drilling rig.
I drink every drop from a can/bottle, usually, but I am a bit wasteful in the kitchen sink and probably only half the tap water is swallowed. Not to mention my dishwasher uses 5 gallons or 10 gallons or whatever small number every time it cycles and washes my drinking cup (so my drinking cup's share is only maybe 1/2 cup of dishwasher cycle water, but, maybe I was only thirsty for 1/2 cup of water leading to 50% efficiency right there). And of course the dishwasher uses electricity (water) and detergent (water) and natgas to heat the water (contaminated fracking water).
I bet using the usual journalist sophistry techniques I could get your home sink up to 10:1 ratio pretty easy. Maybe not the hundreds to one ratio in the article, but close.
But I get your point about the entire construction of the well. And the drilling rig, say it drills 500 wells in its life span. Then you have to consider the water that went in to building the rig, divided by 500. And the water that goes in to disassembly and recycling. And the water that went in to building the drill rig factory. And that went into building the tools that were used to build the factory. Etc.
The world is insanely inefficient, and those inefficiencies are REAL even if we have been that inefficient since prehistoric time. All of the points you mention are actual opportunities for improvement, and a 1% reduction in any of them would amount to an enormous savings in water use, fuel use, increase in long term profit, etc.
For some of us, it's irritating of course: the program takes a long time due to the attempts to save water, and we have no shortage of clean water here whatsoever, so time is wasted to save water which could be wasted.
Do you have any sources for this? I have never heard a vegan claim this once.