No it isn't. CA will still try to tax those shares if and when he decides to liquidate them. However, Musk does not ever need to liquidate any shares. If he never wants to pay any tax, all he has to do is buy a hedge against the shares (thereby locking in a particular price) and take out loans against the now hedged asset. And like magic, he's got all the cash he could ever need and zero capital gains.

Can I do this with my vesting stocks? I get tax deducted stocks, always!

You sure can. You just need to find a bank/broker/anyone willing to lend to you against them as collateral.

…but how does he pay back those loans?

His estate pays them back when he dies. Inherited shares have their cost basis reset to the current value, so if his heirs sell them immediately there's no capital gains to be taxed.

The loan will be cheap but not free. The problem with shares is that their price can go down to zero in case of company bankruptcy. So there will be premium for that risk.

Not really. His loan will be way way way way over-collateralized, and like I said, he can even hedge it perfectly. His cost will likely be about the RFR.