Isn't this what proper framesets (not iframes) were supposed to do a long time ago (HTML 4?). At least they autoexpanded just fine and the user could even adjust the size to their preference.

There was a lot of criticism for frames [1] but still they were successfully deployed for useful stuff like Java API documentation [2].

In my opinion the whole thing didn't stay mostly because of too little flexibility for designer: Framesets were probably well enough for useful information pages but didn't account for all the designers' needs with their bulky scrollbars and limited number of subspaces on the screen. Today it is too late to revive them because framesets as-is wouldn't probably work well on mobile...

[1] <https://www.nngroup.com/articles/why-frames-suck-most-of-the...> - I love how much of it is not applicable anymore and all of these problems mentioned with frames are present in today's web in an even nastier way?

[2] <https://www.eeng.dcu.ie/~ee553/ee402notes/html/figures/JavaD...>