No! You aren't getting it. Software rendering is what X11 uses. It works exactly the same as Wayland. Unless it's hacked with the ported version of Chrome.
You summarized your own ineptness best in your own statement.
And as can be seen in my screenshots, CPU usage is at best 5% lower using hardware rendering as opposed to software rendering - Meaning heat output should be, effectively, identical under software rendering vs hardware rendering. Now you were quoting considerably higher differences than that under Wayland regrading CPU usage considering software rendering vs hardware rendering, were you not?
Because if you weren't than your opening post isn't very clear. Furthermore, if you weren't than your claims of increased heat output make no sense as CPU usage is literally identical under both scenarios. Wayland is not the default for Gnome 3, like KDE Wayland is a tech preview - Wayland simply isn't finished and is a work in progress. In comparison to Wayland the fact is X11 is a polished masterpiece, Wayland has all sorts of quirky issues.