I think I have figured out what he meant.
AMD cards are affected but Epoch changes. With every new epoch the hashrate of AMD card drops. Red rigs losing profitability on every 3rd day. NVidia cards are not affected.
With a fix of the driver AMD rigs will improve hashrate. It will consequently cause difficulty spike. Nvidia will lose profitability.
AMD will gain profitability as the improved hashrate and profitability will overcompensate the loss due to the difficulty.
If I am right I am very impressed by that guy putting such a complex explanation into 6 words

He is also wrong that NVidia rigs not mining ETH. They do.
With the AMD driver fix, AMD cards just regained the hashrate they lost from the increased DAG filesize while NVidia cards gained or lost nothing (NVidia cards' hashrate won't change even up to DAG 190). Status quo pre-DAG increase was just restored. Everyone is affected by the difficulty spike whether it's AMD or NVidia cards.