The plural doubling isn't necessary if you can tell from the context that the word is plural. So you could say 'dua hotel' (two hotels), rather than 'dua hotel-hotel'. In this case it's more subtle, but I think it's the same reasoning.
I answered "those buildings are a hotel" and got it wrong. Wouldn't that also be correct? (many hotels consist of multiple buildings)
It should be acceptable and worth reporting as this Bahasa sentence could easily be referring to a single hotel composed of multiple buildings.