I've got a set of bullet proof alloy DT Swiss wheels I use for bikepacking/touring on my gravel bike and I wanted an extra climbing gear for when I'm loaded with gear. Thankfully you can adjust a GRX rear derailleur to accommodate an 11-40 rear cassette.
I replaced a worn DuraAce cassette with the Shimano M8000 for more durability in winter months. The fit and efficiency is excellent and Ive not noticed any issues in shifting. Great recommendation for the swap by Seth! Thanks again!