Transmitting your hardware serial to Apple along with your direct IP permits Apple and anyone with access to Apple's databases/logs a record of your travel history, because IPs are city-level geolocation.
Macs and iPhones also maintain a persistent connection to the Apple push notification service with a TLS client certificate obtained via registering with the hardware serial.
Just because you personally are okay with Apple and, by extension, the US military having your travel history doesn't mean that there's no problem with it.
I honestly see no problem with Apple knowing the IP address. It’s the same with Windows 10, since it will check for Windows updates frequently.
If you see these things as a problem it’s probably best to use Qubes OS instead.