Shouldn't it also accept 'The kitchen tent is white'? 'Tenda' translates to tent and a kitchen tent does exist because I have been in one. It's a tent with tables, stoves, pots pans and food and funnily enough it is also white.
In order for "kitchen tent" to work, the italian sentence should have been "La tenda-cucina" or "La tenda adibita a cucina". "La tenda della cucina" clearly states that we are talking about the curtain OF the kitchen, it can't be the tent OF the kitchen.
You are literally correct, however in English one would normally say "kitchen curtain". Usually DuoLingo is also very literal in their translations but here they are thankfully giving us the normal translation.