Please explain to me how you can't achieve your desired stock exposure by receiving cash and then buying stock on the public market with that cash?

Kind of irrelevant because you will likely never receive a cash comp package equivalent to your salary + RSU amount. If it were that simple, virtually everyone would take the cash.

This entire thread is discussing the hypothetical where you could exchange your stock comp to cash. People upthread were claiming that the stock is more valuable, even though cash is exchangeable to stock without limitations, and the opposite is not true. You yourself said "virtually everyone would take the cash", so I take it that you agree with me.

I think you misunderstood, it's not that stock is more valuable, it's that you should opt to cash+stock because the total value of this will be higher than a pure cash offer. Essentially, cash and public stock is the same to an emplloyee, but for companies, paying in stock is better for them.

Let's say you know you will get a bonus that pays out end next year worth 10k. You can chose to receive 10k cash or 10k of google shares at today's prices. Most would trade the risk for potential upside.