iPhone, is Reset Network settings necessary after a Carrier profile install?
No, you don't have to reset the network settings. Your phone carrier is just being thorough, as updating the profile can result in some unexpected behaviour for some users and resetting network settings usually resolves this.

I've personally only ever had to reset network settings once on an iPhone after a profile update, so you can just install the new profile and reset network settings afterwards if you start noticing some weird behaviour.