Not so much, in my opinion. We should be careful with translating prepositions as separate words. They don't always align exactly. Partly because prepositions are part of the behaviour of a verb and that can be almost arbitrary. Signing for someone to receive their parcel, for example, I would say לחתום בשם מישהו, or בשם מי אני חותם?. Or maybe, בשביל מי אני חותם?. I'm not absolutely sure what is meant here, but it could mean, I am a celebrity giving autographs, give me your name so I can dedicate my book to you etc.. Or maybe, who is the person with the form that I am requested to sign?
למי אני חותם, in translation apps:
Microsoft = Who am I signing? Google = Who am I signing for? Reverso (app) = To whom I sign? (dictionary translator, context translation couldn't find it written as a phrase in their media database (mostly movie scripts or similar I think) , they only had אני חותם,
But it doesn't always match up exactly when translating... and their English translation is incoherent. We frequently have to add words to make the English translation understandable anyway (is, are, do). I see no other way to make this sentence translate to English. I'll put it through translating apps and see what they say.
Is the idea that I am making out a check to someone, or signing something in favor of someone? It would never be phrased like this in English. The Hebrew duolingo team needs some native English speakers, not just Israelis who lived in New York for a while and think they know the language.