The problem isn't how risky your career at Google is, it's about the correlation of that risk with the risk of your investments. The most likely risk of working at Google is if you lose your job. Well losing your job is highly correlated with whether Google lays loads of people off. Which is highly correlated with the share price collapsing. Which is highly correlated with the tech sector crashing.

So most likely scenario for that risk to materialize involves: Google runs into trouble so needs to lay people off. So at that point, you've lost your job, and all your investments in Google are down for the same reason you lost your job, and because Google is such a large company it's layoffs mean a flood of talent into the labor pool so your future job prospects are effected.

So your safety net of savings becomes far less valuable at exactly the time you use it most.

It almost doesn't matter how safe you think Google is - because by working there you're already massively more invested in it than almost any investor would be.