After reading this forum, 2 months too late unfortunately, I am sitting in a Chevy dealership with the exact same "whine".
My wife and I purchased a Certified 2018 Traverse Premier with 22k miles 2 months ago. A random high pitched whine while holding the break started 2 weeks ago. As of last week, the whine is heard even in park, lucky for us we have warranty and the Chevy associate clearly heard it coming from the engine. I recorded multiple videos just in case the "whine" couldn't be heard at the dealership. Haha
If anyone has had this issue and it was resolved completely since 2018, please share. I do not want to have to deal with the same issue for years, especially after our warranty expires.
Will share more if any future issues arise, especially since I read about the already documented Shift to Park issue this vehicle has as well.