Not true. Game devs can optimise for hardware other than Nvidia.
http://wccftech.com/nvidia-gameworks-amd-both-sides-analysis/3/
What you said doesn't change the fact that he was talking about AMD optimizing.
You're talking about Game Devs optimizing. So what he said is in fact true.
What you said is also true.
@OP
This is something we have all had to decide on if you chose an AMD card.
From my perspective (As I CERTAINLY am not stupid enough to talk in absolutes) this is how I see it in general terms:
-Gameworks titles are broken on release for AMD cards. Day 1, AMD performance just isn't good. It may be the whole game, or a specific setting.
-As the title is out longer, AMD gets patches in and the title usually is playable or even AMD may be faster in the long run.
-Some games still suffer poor performance (I honestly can't name one other than Project Cars?) or don't allow crossfire which hurts if you want to go high end.
-Gameworks specific features are MASSIVE performance hits. This is one thing I'm not sure why it is not talked about more. The specific features like Hairworks for example are very hurtful to performance on mid high end GPUs. You won't even use the futures most likely due to how much it will hit your FPS. Unless you're at a GTX980Ti level GPU, I'd say you'd be better off waiting whether you're AMD or Nvidia user on a Gameworks game until it has received some patches.
Anno2205 while I'm not sure if it's a GW game, it's the typical broken GW game performance.
It takes a GTX980Ti to get just 60fps max settings. If not, you're at a GTX 970 with 30 FPS or so? Is that what you're happy with? I'll wait for the game to be fixed, AMD or Nvidia because even if I have a 980Ti, I'll prefer to take advantage of my high refresh rate screen, or use my 4K monitor. You don't pay for a GTX 980Ti, and get excited for 1080p/60fps gaming.
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Should this deter you away from AMD? Sure, if you play a LOT of PC games, and feel GW titles are a must play at release.
That is the conclusion I have come to. That when it comes to GW to me in picking between AMD and Nvidia, it really doesn't matter to me, because sure, Nvidia has better day 1 performance, but the day 1 performance of 30-40 FPS on a GTX 970 on max settings on a game just isn't appealing to me either way. 1080p 60 fps isn't what I'd spend $650 on a gpu for.
Look at Anno2205 as an example and decide if you think it's worth it to have a GTX 970 to be able to play that game TODAY at those settings/fps. If it is, go Nvidia for SURE. If it's not worth it, and you'd wait, then AMD and Nvidia are still both options for you!