Yes and no. Basically the old benefit of 51% is "few confirmations" accommodating a split for a double-spend. With Avalanche, network control can cause a sway. But remains _not_ split.
I understand that, I'm saying they were proposing using PoW over the last 100 blocks as a selection mechanism for Avalanche instead of PoS
Just that centralization or any kind of attack would still rely upon gaining a large majority of hashrate on the network. Lots of people were irked by the idea of PoS Bitcoin