Dispenser Fire Charge not igniting from below

Fire charge mechanics seem to have changed in 1.13. You used to be able to ignite blocks from below by shooting a fire charge out of an upward facing dispenser. The block directly above it, if flammable, would catch fire. Now, the blocks no longer ignite. I used to use this for fire traps: you could hide a bunch of dispensers underground and then the floor would have the appearance of spontaneously bursting into flames.

Additionally, the fire charge shot upwards from a dispenser no longer ignites any blocks above it, even several blocks higher. For example, if you shoot a fire charge vertically up at a tree, it will not catch fire. Fire charges shot horizontally from a dispenser, or downward, still cause blocks to catch fire. It's just the upward mechanics that are cramping my style. Do we know if this was intentional, or if it's a bug? It was a useful mechanic and I don't understand why it would be changed.