Quoted from rubberducks:Castle doors are reliable, they just significantly add to the difficulty of the upper pf. Very few people ever complete rescue mb and qualify that part of the final wizard mode. If they are removed, it likely means a software option will be added to older versions to have them open. Personally, I'd give a 3 second ball save when you get the ball up to the upper playfield during multiballs, instead. But I think they'd like to combine potential game balance improvements with cost reductions. There's already an option to have monkey virtual locks.
Personally I'd eliminate the OLED on the crystal ball and add some addressable RGB lights.you have to look at it from the right angle to see it, and never look at it during play. It was more useful in early code before all the other audio visual clues were in. It's totally redundant now.
Most players may not get to the step of collecting the Super Jackpot but not having the castle doors would require more of a re-write to that code than just that because as it is if you hit the ball in there with any of the letters lit it gives you the other jackpot (can't remember what it's called) and resets your progress towards the Super Jackpot. It's also a way to add two letters and an arguably safer way to light some of the letters just to enable Rescue MB start. I don't know why they would remove them other than cost savings but that code work time could easily offset their savings on the BOM.