They are separate. Under the "Find My iPhone" setting there are separate toggles for "Find My iPhone" and "Find My network".

If you enable "Find My iPhone" but do not enabled "Find My network" you can only find your phone when it is online.

Enabling "Find My network" to make your phone participate in the "Find My" network lets you potentially find your phone when it is not online.

Same with "Find My iPad".

Sorry for getting the terminology wrong. I don't use iPhones.

I meant coupling the "Find My network" feature for iPhones and AirTags.

It's not really coupled. It's more of a quid pro quo relationship.

There are two separate "find lost things" systems.

1. There is a system for finding online things. This is available on devices that have internet connections, and can only be used to find the device when it is online. The device uses its internet connection to report to a central server, which can then tell the owner where to find the device.

2. There is a system for finding things that aren't online. Devices that do not have an internet connection can use this system to let nearby devices know they are there. If those nearby devices have an internet connection, they can relay that sighting along with their location to a central server, which can then tell the owner where to find the missing devices. The relay to the server is protected by some clever public key cryptography so that the server doesn't find out whose device spotted the missing device or where it was.

An iPhone is capable of using both of those systems. There's a toggle for each of them in the settings.

If you want to be able to find your missing iPhone when it is offline you need to use the second system. If you only need to find it when it has an internet connection, you just need to use the first system.

It seems pretty fair. If you want to use other people's phones to find yours when it is offline, you have to let them use your phone to find their offline devices.