Sofas don't drop the item when broken with a tool or hand, they simply vanish.

To reproduce: just place down a sofa (I was using Cyan, but also tested with White, Orange, and Red) and attempt to break it in survival mode.

Please complete the following information:

• Minecraft Version: 1.15.2
• Mod Version: 7.0.0-pre16

Unfortunately it's unlikely that the 1.15.2 version will receive more updates. This has been fixed in 1.16 version though.