"The poi is in the bowl."
Translation:Aia ka poi ma ke pola.
It is not wrong; it is a nuance. I think DL sees the better alternative to the preposition as "ma" because it implies "within" rather than "to" or "at." "Hana au ma Honolulu" I work in Honolulu. "Hana au i Honolulu," I work at Honolulu. In conversation, few people would care. OR, maybe DL forgot to include "i" as a correct option.
Words beginning with k, e, a, o are preceded by the definite article "ke" for the. Most others are preceded by the definite article "ka" for the. But there are exception where "ke" is used instead. There are not many, but when they occur they are most often before a word beginning with "p" or an 'okina (‘). Some words mean one thing with a "ke" and something else with a "ka" such as: ke pā = plate. ka pā = fence, enclosure, yard. Some of the exceptions are: ke puna = spoon; ke pola = bowl; ke pākaukau = table; ke pā = plate; ke po’o = head, summit, director; ke ‘ala – fragrance, perfume; ke ‘ano = type, kind, variety; ke ‘eke – bag; ka or ke mele – music, song. Hope this helps.