On Minecraft 1.12 Pre Release 5, Which Has Been On My PC Since Snapshots, The Hardened Clay Has The Names Of Terracotta like "Pink Terracotta" Or "White Terracotta". This Has Not Affected Texture Of It Or Anything Else, though. This Has Lingered Since Snapshots Released In April/May I do believe.
MC-117801
Name of stained/hardened clay is messed up
Resolved
Duplicate
0
That is not a bug from what I can tell.