Thanks so much for posting this. I can say that at least at
Disneyland Half this year, they already had us pass through a bag check if you walked from a hotel on Harbor Blvd to the corrals - the same bag check to get into the parks. There were no lines at 4:45am (per my personal experience). And yes, bag check at Disney includes race belts (again in my experience).
But this sounds like they are adding some other check point that'll likely cause bottlenecks over in Downtown Disney. Glad we at least have some idea about this. Feel bad for those who won't pay attention to the emails or check this out on message boards like the Dis. I feel like a lot of folks are gonna end up arriving to their corrals even later.
I hope Disney puts out some kind of reminder on social media for those who didn't get or didn't read the email. But based on the spartan social media coverage of the race, I'm guessing that may not happen.