Firmware update to what exactly? If you mean to the keyboard’s embedded controller chip then yes that would probably do it but I don’t think Purism can do that. No source.
If you mean to the BIOS, I think it is more complicated than that due to the number of different environments that all have to work: BIOS x 2, GRUB, early boot, LUKS, live boot (various distros), Qubes, PureOS, other distros
It was stated that this will be fixed by a new model (v5, using a different keyboard embedded controller): Keyboard layout unable to recognize pipe - #55 by MrChromebox
Obviously it is awkward that the ‘|’ character is so frequently used by anyone who uses a shell but, as the above-linked topic notes, you can be in strife if your LUKS password contains this character.
It is also implied in that topic that they have upstreamed a quirk accommodation for this but maybe that was after @zenbum bought the 13v4.