Too bad they didn't try to implement a reliable automated primer feed system.
More speculation from me.
I think Auto Breech Lock Pro (Pro 4000) probably was under development for quite a few years and during that time, I bet Lee considered and evaluated many different priming options.
With Pro 1000, there were many complaints from users and Auto Breech Lock Pro (Pro 4000) has features from other presses likely to address those complaints like Breech Lock for dies, steel base, through ram spent primer disposal, index rod for shell plate (which is also on the 2018 model of Pro 1000 along with steel base), etc.
The priming system there looks just terrible.
Welcome to THR and join the club on safety prime for the new press.
The fact that Auto Breech Lock Pro was released with the safety prime tells me they could not find a better priming system and they defaulted to a priming system that probably performed the most reliable from their testing. (Maybe John Lee is having second thoughts about using Safety Prime?)
As a Pro 1000 user, I too hoped for a better automated priming system but we got safety prime and we either have to like/accept it and buy the press or hate it and buy a different press. That's our choice.
If my initial testing goes well, I am planning to use the Auto Breech Lock Pro (Pro 4000) as my reference press to replace Pro 1000 (Yes, I load all of my test rounds for various THR threads on the humble Pro 1000 press with occasional exception when I use C-H 205 single stage press). Which means, based on my various myth busting threads, I will be sorting brass by headstamp/case wall thickness/resized length, bench priming and using pre-resized brass for my future test rounds to reduce reloading variables and better standardize testing methods.
So safety prime is not a deal breaker for me, but it could be for others.