I'm fairly sure that these very low numbers for median tenure (not just for Google but the other tech companies as well) are a result of the huge percentage of new hires. That number does not mean that the average Google employee will only be at the company for 1.1 years.
e.g. if nobody ever leaves the company, but you always double the number of employees every year by very aggressive hiring, the average tenure according to that metric is 1 year.
I don't think Google's hiring is increasing fast enough to explain the low rate. It looks like they increased about 10% from 2019 to 2020.
However, it's also unclear exactly how 1.1 number is calculated. It looks like it comes from PayScale, which doesn't give, as far as I can tell, a methodology:
Is that the median amount of time that all current employees have had with the company so far?
Or is it the median of all of the employees that used to work there & moved on, which would exclude people that have continued to work there?
Or is it some type of survival analysis that takes such factors into account?
It's anecdotal but my understanding as someone who hasn't worked there is it seems like either people leave < 2 years or have no plans whatsoever of ever leaving.
e.g. if nobody ever leaves the company, but you always double the number of employees every year by very aggressive hiring, the average tenure according to that metric is 1 year.