Mobs can’t spawn in lower bedrock layers.

In 1.13 bedrock breaking with dragon eggs was removed. I think that bedrock breaking is very cheaty and I understand why it was removed, but I still occasionally use it to make mob farm more efficient. If the spawning algorithm started higher (above bedrock) the a) mob farms would be more efficient and b) people would not need to break bedrock for efficient mob farms. Efficient mob farms would still be a big grind (render distance perimeters, a lot of block placing, maths for portal farms etc.) but would not use the cheaty mechanic of bedrock breaking. I don’t understand programming much (I’m just a beginner) but I think the best way to do it would be to start the spawning algorithm at y=5 in both the overworld and the nether (the end could keep the current mechanics) and so bedrock breaking would not be necessary.