Apple recently updated its iOS 15 feature page, indicating that Find My network support for AirPods Pro and AirPods Max will be delayed a bit - the page states that it will be released "later in the fall", implying that the feature will not be available with the initial release of iOS 15.
Apple did not give a specific reason for the delay, but several other features iOS 15 will not be immediately available, such as SharePlay, Legacy Contacts, the ability to add a driver license or ID to the Wallet app, and more. Apple last month listed iCloud Private Relay as a beta feature.
If you miss your AirPods Pro or AirPods Max and someone else with an iPhone, iPad or Mac approaches, Find My network will be able to transfer an approximate location of the headset. The Apple Find My Network feature is designed to help you when you are within range Bluetooth of AirPods, to be able to play a sound and locate them.
IOS 15 will be released tomorrow after three months of beta testing. The software update is compatible with the same iPhone as iOS 14, including older devices such as the iPhone SE and iPhone 6s. IPadOS 15, watchOS 8 and tvOS 15 will also be released tomorrow, while the release date for macOS Monterey has not been announced yet.
Source of information: macrumors.com