While this is technically true, it's always been technically true, even when those in the religion of the SPA claimed it was clearly faster to use CSR over SSR.
This is just realigning what many of us already knew, SSR is faster.
If I may, the argument of "well... sure, but CSR can be plenty fast!" is redrawing the line after someone stepped over it.
Really it is a lot more about how much stuff you load than how you do it. CSR can at times provide savings, for instance by doing fake page changes and not having to load menus and stuff when the content changes. But of course you have to keep the JS light in order to not eat the savings.
This is just realigning what many of us already knew, SSR is faster.
If I may, the argument of "well... sure, but CSR can be plenty fast!" is redrawing the line after someone stepped over it.