What's the purpose of removing an iPhone from Account in icloud.com > settings?
I do this when I have a device that is lost or stolen. I’ve already documented the serial, filed a police report, sent a remote lock or wipe command. Now it’s time to remove it.
I never expect it back, but Apple has my back and will notify me if it ever comes back online.
I also have some older devices I keep for sentimental reasons. They go in airplane mode, get charged to 50% and powered off, I wake them every 6 months or so to prevent deep discharge of the batteries. No need for them to clutter my list, but they are still under activation lock and my account.