Is there a way to disable this "often used with" prompt on an iPhone?
I believe if you turn off “Siri Suggestions” you will not see those.

https://support.apple.com/guide/iphone/about-siri-suggestions-iph6f94af287/ios

Option in on app usage patterns lets the “neural engine” process app history and look for patterns to suggest. I also find if you dismiss these, Siri sometimes takes the hint and stops suggesting things if you never tap in to use a class of recommendations.
I’ve also found it handy to leave these enabled but “bench” a few specific apps I never want suggested, indexed or searched.