During the security delay the phones location is not available on icloud.com. I can’t think of why that would be the case - In my mind if the device is stolen the thief would begin the security delay. It is a great way for the thief to temporarily disable the the find-my service.
They’ve changed that with iOS 17.4
Users can now choose to always require a delay when changing security settings, not just when away from familiar locations.
Personally I’d prefer the option to manually set “safe locations”. I don’t want a delay when I’m at home, but I also don’t want to make things easier for a thief just because my phone thinks it’s in a familiar location, like work or my usual grocery store.
I even enabled advanced data protection on all my apple devices Mac,Ipad,Iphone and addded my emergency contacts incase I get locked out. Apple is very highly secure technology.