Yes, for the most part it is unreasonable in today's macOS environment. It's not that these apps need to “phone home” by the traditional definition, rather they must also stay up to date on malware definitions to be effective against the ever-changing malware types and variants. If you have privacy concerns, check the developer's policy to see what, if any, information is being passed to them. If they require registration, then that's the minimum check that needs to be made when used.Ironically, the take-away for me from all this was that anti-virus software remains difficult to distinguish from the threats they are supposed to protect us from. None of them would function without being given carte blanche to phone home. In spite of preferences seemingly to the contrary, none of them would simply run when asked. They all insisted on daemons in the background. Is it unreasonable to expect these folks to be sensitive to this?
Background processes are necessary to provide real-time / on-access protection involving newly downloaded / changed files. They also control all scheduled scanning and definition / app update checks. And, they are necessary to provide a menu icon.
There have been a couple of requests to ClamXAV to eliminate all background processes as long as Sentry and all scheduled events are disabled. Although such settings are not optimal for providing full protection, the developer has agreed to provide such an option for users who demand complete control in a future release. This will simply eliminate the menubar icon, which uses practically no resources at all, but should satisfy such purists.