Yes, but to be fair to RSUs, this is no worse than having some additional ordinary income.
The 50% on receipt number comes from your marginal federal tax bracket plus state -- same as if the dollar value were additional gross (pre-tax) income.
The 20% on growth number (potentially 25-30% including state) is what you'd pay on capital gains -- same as if you'd taken this extra income as cash and invested it in anything.
