This sounds like a lot of work to me to address a problem that only impacts 0.1% of players, and KeyboardEvent.code looks pretty obscure.
There are entire countries with different standard keyboard layout than QWERTY, I'm pretty sure that 0.1% is inaccurate.
I also remember that some desktop games handled alternative layouts just fine by default, without reconfiguring key bindings manually. I was only ever affected by QWERTZ, so the impact was limited.
Apparently both desktop and web has the suitable API to handle this well, yet web games don't seem to care.