Thats true but I feel duolingo does this so it forces your brain to start thinking in the language. Rather then being walked through every step it throws new things at us for us to interpert and hopefully precieve it to be the right thing. This method of learning isnt the only way but is the way babys learn languages and its been studied to be the most effective because its hard for your brain to forget something it figured out on its own rather than being told information and a 50/50 chance of that actually staying in your mind.. good luck :)
"The cook has a kitchen" would be useful in a situation where someone hires a cook and wants to know if he needs to provide him a place to do his work. In that case, "the cook has a kitchen" is the appropriate response, as if to say, he is a caterer and has everything he needs.
"The kitchen has a cook" is different. An unemployed cook scouting out a place to see if they will hire him, might ask questions about the kitchen. In response, he might be told, "the kitchen has a cook," iow, we don't need you.
Two different sentences, two different meanings. :)