You’re making a big bet on equity appreciation though. That’s how the vast majority of very highly paid folks in tech make their money. The consulting jobs pay it in cash.
That's the point, you don't know whether there will be any. So they are definitely not "as good as cash". Just because they aren't lottery tickets doesn't mean they are equivalent to cash.
Edit: Just to clarify, $300k as a senior engineer is without any stock appreciation at all. I made $250k as one step below senior without any stock appreciation at all. My point about significant stock changes is for significant stock changes downwards, meaning if the Google stock somehow lost 50% of their value or something like that.
My point was a more holistic view. It's great that there is a 95% chance that your stock RSUs will increase. But if there is a 90% chance that within 3 years it's a 15% increase or more, you should rather use the 15% increased figure for calculation instead. And then the risk is much higher because it's not just stock not going down, but stock not going up as quickly as it did before.