It is more common now. I've seen two implementations of it:

• The board has an A and B ROM, which are both treated with the same priority, and a button that switches which one the PC boots from. You can reflash the one that's selected. With this it's actually practical to have two different BIOS/UEFI builds and switch between them, but to be honest that's rarely useful unless you're testing/troubleshooting related stuff. It's usually labelled "Dual BIOS" or something like that.
• The board has a primary ROM and a backup. It only ever boots from the primary, but if POST fails you can push a button to reflash the primary from the secondary. The secondary backs up the primary when there's a good POST, usually automatically and not user configurable. It's usually labeled "backup BIOS" or something similar.

These are not standard, and not major selling points, so different manufacturers have different implementations and unfortunately different names for it. You have to do some reading, and it might not be mentioned in the product listing, you might have to find the manual to read the full specs. Your motherboard might even already have this feature without you knowing it. Does it have a button like this?

Or this (the BIOS_FLBK one, not the CLR_CMOS in the red box)

If you are buying a new board, the little two-digit display in that second picture is also a nice feature. It's a POST error code display. Rather than just getting some beeps during a POST failure, it will give you an error code that you can look up to figure out what the specific problem area is (e.g. RAM not fully inserted, clock mismatch, etc).

Usually only on top end mbs. Some cheaper ones have a bios recovery tho, which should achieve the same results

Wait, that is such a good point. Why aren't motherboard firmware updates atomic?

Hmm, my motherboard (Asus) just has a reset button that flashes the contents of the secondary ROM to the primary ROM. If there's any problem getting the primary to POST, you just push the button and it reflashes the primary from the secondary, so you're back in the original state. It's not a one-shot, because the contents of the secondary don't change. You can use it as many times as you need to.

Once you get a good POST from the primary, it updates the secondary. I've never had an issue with this system.

Phone mainboards are very different, which is a big part of why maintaining third-party phone OSes is such difficult work, and why GrapheneOS constrains itself to specific devices.