Note the complete lack of PINx register emulation which makes it even less useful.
I can’t imagine when this emulation thing is useful.
Either the normal functions and libraries work well enough, or you want to get more out of your processor.
If you buy a better processor (for example 4809 over 328) you most likely do that to use the improved capabilities of it.
In both cases you’ll need to study the register structure.
Reversing the view: people that use the direct access to the registers do so with a purpose and with knowledge, and will be thrown off their game by this emulation thing.
Some of the libraries use registers. I think the hope was that the "register emulation" would allow more of the existing code written for the ATmega328P to be used with the Nano Every.
Or they are using a library or a sketch they found on the Internet and just want it to work with the board they bought so they can get on with their project; not knowing or caring anything about registers or about performance as long as it works well enough.
Like a band-aid for programs that are written for not your processor.