Looking at the poll results, if you get in the park on time, the odds are pretty good you will get a BG or BBG.
The folks on here are more likely better informed and prepared for getting a BG but it looks like if you are in the park on time, odds are pretty good you get at least a BBG.
I have to imagine that WDW for the moment likes this system. Having all guests go through the tap stiles before opening gives them a rough number of how many people seriously want to ride. The early morning start and having everyone get through the gates per-opening, creates a natural limitation on the number of available guests, maybe below daily ROTR ride capacity.
Since most people get a BG, I’m guessing that they know there are X number of people and allocate the number and size of the Boarding Groups so that they can try to accommodate as many of those people as possible. Guest Services doesn’t want to have a large mob of angry people there at the park at the start of the day who did everything “right” and still didn’t get at least a BBG.
I have not seen a lot of news reports or social media posts complaining about this. The polls seem to confirm it. If large numbers of people were getting rejected first thing in the morning there would be a major blow-up. Maybe I’m wrong in my thinking. It’s just this fool’s opinion. I haven’t tried yet personally but I’ll be there in April to see first hand.