You are paying for the most expensive item you will ever own and you have to "compromise" with your woodwork finish? Why? Why allow your designer to decide what you have in YOUR house when that is NOT WHAT YOU WANT?
I am an interior decorator and I pride myself in giving my clients what they want, not what I want them to have. Sure, if I see they are about to make a mistake, I will make a suggestion, but I would never inject my own personal desires upon them if they otherwise express a desire for something else. ESPECIALLY mixing finishes on interior woodwork.
This is your home. After your designer is done with your job, she moves on and is off to other conquests while you are in your home and unhappy with the mixed woodwork finishes.
I added 1200sf to my cottage. The cottage part of the house has all painted woodwork and the addition has stained and polyurethaned woodwork. I compromised with the husband as he wanted the stained wood work, not me. Here I am, 30 years later and I still want my white woodwork. The husband is a wasband and those choices were a wifetime ago. So, I am painting everything white. It is going to be a hard job because of the poly finish I need to eliminate so the priming and painting is successful.
My experience gives me wisdom and I wish I had the woodwork white all along. I would never consider mixing two different window finishes in one room. Howsoever, I did decorate a beach house where the husband and wife differed in the finishes on the windows, so I put on my clever hat and got THEM to compromise. They came to an agreement to have the woodwork painted white and the SILLS all finished in a beautiful Gunstock stain with a high gloss poly finish. It was beautiful, just beautiful.