I'm going to throw a thought into the mix on this that I haven't seen talked about. I am ignorant as to how the HUD is/isn't LINKED to the Nav. It occurred to me to wonder: if I get
Apple Car Play in my 2015 Genesis 3.8 Ultimate with its 9 inch NAV - in case specifics are relevant - and I choose to use/mirror Waze, for the HUD to work either it would have to be able to pull the relevant info and routes from Waze to mirror the app, OR you would have to simultaneously run the address through the Nav and HOPE it followed Waze' route - I can tell you it does NOT happen a lot ...
So you are faced with giving up a move to the future or losing an expensive critical feature of our cars and have to choose and I can tell you that would/will be a TOUGH decision.
Mind one could run the address through both systems and follow HUD where it works and when you notice it isn'/t the same follow Waze .... yeah, I think you can see the problem here!
So I'm going to guess that it might be connecting the HUD to third party GPS apps that's stalling availability as that is a hardware feature NOT available in most cars and thus the software for linkage would be unique. By which I just mean every car has a radio, USB system so much software is reusable or adaptable to different Makes and models etc. not with this ...