Podzol Texture Bug

Not to sure if this is a bug or not, but I decided to post it anyway.

When you place a block on Podzol, the Podzol texture instantly turns to dirt. When you remove the block that's on the Podzol, the regular Podzol texture replaces the dirt texture. This only happens when Dirt, Podzol or Grass Blocks are placed on Podzol. This effect does not happen on Grass or Mycelium.