Deep slate not generating below y level 0

This glitch was on the same world where I found the azalea tree underwater. So as I dug under the tree I found a lush caves biome so I explored and decided to dig Down and see if the devs made the bedrock lower they did but for some reason there was no deepslate so I checked the surrounding area and there were only blobs of deepslate no complete deepslate at all below y level 0