He's kinda right even though he's kinda wrong.

He's confused about the retribution thing. Korean manufacturers aren't afraid of US to restart DDR4 manufacturing. They don't want to restart it anyway. But I'm pretty sure I've recently read it somewhere credible that they'd normally sell their old machinery but now they can't because they're afraid China would be the eventual buyer (via proxies) and they'd be inadvertently in violation of US sanctions , so instead of selling they just locked down the old machinery to gather dust instead.

And about DDR4 not being relevant, even though DDR4 manufacturing stopped earlier this year and DDR4 prices have been slowly but steadily increasing long before this crisis, after the crisis DDR4 prices have also tripled just like DDR5 prices, even in the used market. So regardless of whether it's a real demand or panic response, the effect is still real on people wanting to upgrade their DDR4 systems. These people who probably just wants to update RAM in their systems in the hope that it'd help them delay their switch to DDR5 systems for a few years while bracing the impact. Had Chinese manufacturers continued to manufacture DDR4 at least this wouldn't be that bad for the existing system upgrades of DDR4 systems.