Ok, I can see your argument, let me repeat it back to see if I got it right.
You argue that by being physically near the Columbia river, a hydro electric plant can be constructed which generates power and sends it directly to a Google data center. But their other properties, some of which are nearer power plants which generate power using fossil fuels can not be considered to be using renewable energy. Is that about right?
If so, I see it a bit differently, if Google builds a concentrated solar plant in the Mohave Desert and that plant puts adds 1200MWhrs of energy to the Western Grid every month, and Google's real estate in California consume 1000MWhrs of energy from the grid every month, I can see that being claimed as using 100% renewable energy. There isn't a specific path of the electrons to the Google buildings but in that scenario Google will have added more energy through renewable sources into the grid than they extracted from the grid[1]
I've got Solar panels on my house and they generate more power during the day than I can use, they generate no power at night. I have them connected to the grid. When I'm generating excess power its probably being used by my neighbors but somewhere nearby a fossil fuel plant is using less fuel because of the power I am feeding into the grid.
Because is is set up this way, PG&E bills me on an annual basis and on that basis the 'net' amount of energy my house uses is quite small, in terms of ratios, over 90% of my total electrical energy usage is accounted for by the energy I generate on my rooftop. I think of that as "90%" of my energy comes from renewable sources, even though every night, at that moment, I'm using fossil fuel sources (or simply the grid). Once I have a couple of PowerWall's install it will get a bit more explicit but I consider both interpretations valid. I'm guessing from your argument that you do not.
[1] You can also argue that the 2nd law of thermodynamics tells us that adding it and then removing it will leave a bit behind so perhaps a draw of 1MWhr might need an input of 1.2MWr in order to offset grid losses to radiation and heat.