You might need to update the modules. The nice thing about bixby is you can always use it while also having google assistant set up all at the same time this way you can use either. Bixby does something's that google can't so that's why I personally enjoy using both. Bixby can do a lot of hands free phone functions.
Hey with the new one ui 6 update they made it work with WiFi calling plus they further improved it by making it possible to go in and out of the bixby call system or switching to voice and you can go back and fourth as you please, that's something even google can't do!!!
I've tried using Bixby for several things and I think the Google Assistant by far as much better something as simple as screening calls can't be done on Wi-Fi and my experience with my 23 ultra
Do you mean the feature that let's you use bixby to answer calls and write text messages to the callers? I noticed that doesn't work on wifi calls as well and I can't explain why but there's likely some reason for it. I do find that strange myself. But I encourage you to use both bixby and Google if you have the ability to use both why choose only one? I have the s23 ultra as well love it. From my extended time using both assistants I can say there are a few minor things bixby does that Google doesn't and vice versa there are some things Google does better then bixby. Bixby is really good at handling routines and on device functions while Google is good with anything that requires a internet query. Theres a lot of youtube videos discussing this subject thats how I learned a lot about both assistants myself.
It takes some getting used to and familiarizing yourself with boxbys functions more so then Google does. Bixby tends to only function properly when you say the exact right phrases where Google can figure out what you mean a lot better then bixby does but again there are still things Google can't actually do that bixby can due to the fact that bixby is actually integrated into the hardware of the phone very well where as Google has to work with every single device out there.
I find Bixby good for performing phone functions, maikg calls, turning on the flash, setting reminders, etc., and Google Assistant for web searches.
Well I'm glad that you folks have better luck with Bixby I've never used Bixby since Bixby came out and when I tried I was pretty unsatisfied I'll remain committed to Google Assistant