It's not anti 99% attack, that simply shows you can't sell 99% of coins and then rewind if there's someone else. You still can force forks if you have >50%, but you can't force a fork if you sold them, because the buyer can also forge.

The whole point is that the cost of such attack is orders of magnitude higher than in PoW, as percent of market cap, especially in later stage, where there are only transaction fees.