I think you are spot on, FORD has said the build order will be dictated on constraints and their build software that directs which trim/models/options will be the most efficient to build on the line for that particular run. It looks like OP likely has one of the first runs...good luckDelivery date depends on so many things, but one of the toughest is option constraints. If your Bronco order doesn't have any of those nasty things it's quite possible you could get yours in '21. But, I don't suggest you hold your breath. Remember it also depends on what the folks in front of you order. It would be a big leap to get into those first 100 the dealer says they'll get.
I do remember my first new car, and I understand the excitement. So good luck. I really hope you can get yours this year.