From a Native Irish Speaker
Today I decided to try Duolingo Irish. I learned Irish before I learned English and I was really bothered when I was marked wrong when I wrote certain sentences For example, when I used 'mar gheall go' instead of 'mar' I was marked as wrong I'm glad that this is a language on Duolingo. I just wish they'd recognized the way people say certain things. This seems to be mainly Laigheann/Mumhann style Irish from what I've done. Maybe a bit more of the Western style? Ba bhreá liom bhur gcuid tuairimí a chloisteáil
Did you report your answer as correct? Assuming it is correct according to the standard, the course contributors would probably add it as correct. As you can imagine, it's very hard for them to get every possible translation written down on their own, so they're bound to have made accidental oversights.
I know for a fact that while the team aims to teach "standard Irish," they want ALL forms of Irish to be accepted. I'm sure they'd be glad to hear your suggestion. They've had a pretty crazy time making the course accept not only multiple dialects of Irish, but also multiple dialects of English!! They do want answers from people like you to be considered correct by the course.