I have a few 'before hours' breakfasts in Jan...I'll be interested to see if there have been any changes. I really don't think there is any way they are going to have CMs escorting people around Main St. People have ADRs at all different times...they would have to have a ton of CMs on duty to escort guests to CP or to CRT.
As far as being in the park before it officially opens, there is little you can do, other than take some photos. There are no shops open, nowhere to get into any mischief. You check in with the CM with the clipboard, then go through the turnstiles, and off to your restaurant. Now...I don't think I would try to get in at 7:45 if my ADR wasn't until 8:30...I think that would be pushing it a bit and I don't think they would allow me in that early. But, I really don't think there is any issue if I show up at 8:15 for that 8:30 ADR.
I think it may have been a case of those being on the tours having to have nametags because they would not have any other reason to be in the parks. If you are going to an early ADR for breakfast, then you have a reason to be there. When I did the KTTK tour in Dec, I checked in at the desk before the park officially opened. No problem. But, we were told not to wander off without our tour guide. Our tour left at 8:30 if I remember correctly, so it would have been before the park opened and it would have looked as if we were being 'escorted'. But that was for the tour, not an early ADR.
But, I'll report back when I return from my Jan trip.