Dirt path and farmland turn into dirt when placing certain transparent blocks on top

Grass Path and farmland blocks turn into a dirt block when putting non full blocks over them.

Affected are:

• signs (you can put them on pressure plates, why not on grass paths?)
• torches (maybe you should be unable to place them on grass paths in the first place)
• fences/fence gates
• doors
• trapdoors
• ladders
• stairs
• slabs