You're right. They're totally different bikes.Dang! The K bikes really changed. That looks nothing like my K100 from 88.
Your '88 K100 was known as the K "flying brick" due to the look of it's longitudinally mounted engine originally sourced from Peugeot. Yup, it was a car engine turned onto it's side!
The newer K bike started with model year 2005. It's known as a K "wedge" due to look of it's transverse mounted engine that's tilted forward at a 55 degree angle.