> RSUs taxed as short term gains and not long term

That's not correct. RSUs get taxed as normal income. So whether you get $600k cash or $300k cash + $300k of RSUs, your tax bill is the same. The gain on the RSUs get taxed as short or long term capital gain. That comes into picture when you sell. If you auto-sell, there is no/very little gain, so no additional tax there and for intents and purpose, it's as if getting $600k in cash.

The numbers reported on levels.fyi are not useless. They give you a good idea of what one can get if they started working there at that moment. You can extrapolate more out of it by understanding the stock gain.