This doesn't make sense since there are stone slabs.
Comments 2
Thank you for your report!
However, this issue is Invalid.
You have posted a feature request or a suggestion. This site is for bug reports only.
For suggestions, please visit Minecraft Suggestions on Reddit or visit the Feedback website.
Quick Links:
📓 Bug Tracker Guidelines – 💬 Community Support – 📧 Mojang Support
📓 Project Summary – ✍️ Feedback and Suggestions – 📖 Game Wiki
None of the 3x3 mineral blocks have a slab variant so this doesn't make a sense.