>The UI for this gets in the way and should only ever present itself if I happen to have both kinds of devices registered.

I disagree. It is very annoying when some service fails to show an option on the grounds that I can't use it. It makes it difficult to resolve problems. If the option is just missing, I have no way to tell whether the company doesn't provide the option, whether the company made some sort of mistake (they can't provide an email option because they lost my email), whether I made a mistake, or whether the company just has a bad UI that tries to hide the option. And don't forget the situation where I tried to google online for some help in using the UI, I found a 6 month old Reddit post showing the option, and I can't figure out if the company changed the UI in the past six months.

They should show it greyed out with a note "no key of this type registered".