He's not blaming Lumen - he's blaming the general trend that a ton of things in the render-pipeline nowadays needs heavy TAA (not reconstruction) to hold together because it's a shimmery mess in individual frames, at any resolution. Lumen is just one of the popular examples - but this is increasingly common everywhere, in most engines. Basically TAA algorithms are doing the heavy lifting for temporally unstable pipelines - with individual frames becoming increasingly lower-fidelity.
As the video mentions, Lumen 'can' be configured to be more temporally stable - at expense of being more laggy - but for a game like SH that's mostly static, especially outdoors in the daytime - that would be a valid trade-off.
Now - the fact that PSSR may not behave as a temporal-stability bandaid is an oversight that someone should have caught - and likely shouldn't be particularly hard to fix - given how it works in analytical temporal accumulators - but yes they shouldn't have been caught by surprise. And if they DID know, they should have insisted games that depend on it continue using other TAA together with PSSR, so neither option is a valid excuse.
However - this should have also been caught before any of these patches went live - noone can say QA somehow 'didn't notice' this - so every single dev carries the responsibility for the state these patches released in as well. It's an incredibly sad state of affairs that game-dev has sunk so low that people would just blindly push 'release' button on visibly subpar updates and be like 'surprise' about it after. I've come to expect that from mobile-apps - but games used to be better than this.