I can't say i've seen a single site where in practice that worked as advertised. Also some times it introduces UX annoyances (e.g. back button not working as expected).
It is one of those things where in theory if absolutely everything was done right and no other stuff was done differently it can work. E.g. if the only difference between a JS-enabled and a JS-disabled version of the site was the content change and nothing else (no additional JS frameworks, functionality or whatever) then yes it most likely can be faster (though for the difference to be noticeable the site needs to be rather heavy in the first place).
Problem being that in practice this comes with a bunch of other baggage that not only throws the benefit out of the window but introduces a bunch of other issues as well.
It is one of those things where in theory if absolutely everything was done right and no other stuff was done differently it can work. E.g. if the only difference between a JS-enabled and a JS-disabled version of the site was the content change and nothing else (no additional JS frameworks, functionality or whatever) then yes it most likely can be faster (though for the difference to be noticeable the site needs to be rather heavy in the first place).
Problem being that in practice this comes with a bunch of other baggage that not only throws the benefit out of the window but introduces a bunch of other issues as well.