Passcode Requirement

See the following from Use a passcode with your iPhone, iPad, or iPod touch - Apple Support

If an alert says to change your passcode or you can't adjust your passcode settings

Configuration profiles and email accounts based on Microsoft Exchange (common with business or education devices) sometimes have passcode policies that cause issues like this:

• You can't turn off your passcode.
• You can't change passcode settings because they're unavailable, gray, or dimmed.
• You see an alert about a Passcode Requirement. For example, you might see a message that says you must change your iPhone unlock passcode within 60 minutes.

Contact your IT administrator for help. If you don’t use a configuration profile or Microsoft Exchange account, or if your device

is personally owned, make sure you update your device to the latest version of iOS or iPadOS.

Does this show up on the lock screen or after you unlocked your phone? I have never seen this message in my 7 years of iOS experience so my gut tells me that this is NOT legit.