If you are in the jungle and you setblock ice with a damage of value 1 you will get a missing texture block and it makes the game look funny. It is weird and it works for some other blocks like: glowstone, sandstone (with value of 3), soulsand, and maybe others.
and giving yourself an item with a damage of value 1, like beacon, crafting table, furnace, anvil, etc. look like 1 side of it like looking at the side like really weird. Anvil looks even weirder. (Damage of >1 for some)
Linked issues
duplicates
Comments

isn't that a bug and what about the second part?

No.
[Mojang] Mog (Ryan Holtz) in MC-49121
If the correct data value is set, then the issue will not happen, so you're basically stating that if the incorrect data value is set, the issue will happen. Not a bug.
All non exisiting blocks get the missingno texture.