Inputconvertion not working for Alternatives

@JBrosi just pointed out in [Course Forum] Genki 1 - Deutsch, that in the associated course the “Normal keyboard Input” (Romanji) does only work for the main solutions.

Say i have a word
English: four
Solution: し (written “shi”)
Alternatives: よん (written “yon”)

Valid solutions are now: し, よん, shi
But this does not work: yon

Is this a know bug?