Creating 20 new accounts didn't give them more influence in the network. Their stake was already there. A sybil attack is when creating more and more accounts will give you more and more power in the network. Imagine a 1 acc = 1 vote democratic system, this wouldn't be sybil resistant, as creating more and more accounts would lead to you having more and more voting power. On steem everything is based on stake alone, creating more accounts doesn't give you any advantage whatsoever.

There's no more or less sybil resistant, it's binary, black or white.

Hope you see my point. I overall agree with your article though, I just think a single word you used is wrong :) What happened is more of a bribe attack (justin bribed exchanges to vote for him to control the network)