That’s a point which has been debated for some time, Rad. As it happens I possess a copy of the story, so wouldn’t have needed the Internet, but still looked at the Wiki version to save time (because I’m lazy).
In principle I agree with you. I can’t see how anyone could have completed 4603 without online help. One could argue that three weeks’ solving time was enough time to look up Grand National winners etc. in a library, although that was hardly possible at the present time!
I suspect that the rule about Internet references is there to discourage setters from themes that can ONLY be researched online, with no other possible resources available. It’s obeyed in spirit, I think, if not to the letter.