Armor of Thorns

I think that it's ridiculous that armor of thorns & it's substance enchantment bretherin do not have flash. If you cast mystical teachings you could not search for them, but all of it's kin, the masques & champions enchant creatures, were errata'd to have flash. In fact, all other instances of "play as an instant" in the game were changed except except for these mirage block auras. I asked around the judge hangouts, and the only answer I could find was that the substance wording was so complicated they didn't want to complicate it more. I don't know if this is the actual reason, but if it is it's a dumb one.