They should just make it 360 seconds for the account no matter what IP as it isn't hard to login on a phone or change your IP with a VPN and bypass this rule.
Does that really work?
Log in with IP 1 and then you can make a post right away with IP 2?

I doubt it. It probably restricts both IP and account wise, simply associating your IP once you use it with an account. Although you can try.
It is a little bit hard for me to test it, considering I need to switch the IP within 8 seconds (my current posting limit) lol.