They've put it out there but It is up to the guest to read what they've posted.
When you go to the how the park reservation system works page, they mention you can hop after 2 and provide the link to learn more about the Park Hopper option there. So the info is there but it puts the onus on the guest to read it. However, as anyone who is responsible for sending out important emails knows, people rarely read the materials they are given, even when it's important stuff such as things that impact employment. Granted, even if you make it very simple and stamp it somewhere obvious, they won't always read it. Most you can do is put the info there and hope some take the effort to read it
Heck, even when they had FP and put the FP info right on the park maps you had guests with maps in their hands who still had no idea the FP existed. I'm not sure what all they can get the word out better.