The /summon (potion) effects for mobs: speed and slowness

With the new command /summon, some (potion) effects that can be added to a mob, are not functional (as I believe).

I was attempting to /summon mobs with potion effects on my multiplayer minecraft server. I was doing this with command blocks. All potion effects worked and were added successfully except speed and slowness.

To recreate this:
1. Put the command:

/summon Cow ~0 ~1 ~0 {ActiveEffects:[{Id:1,Amplifier:10,Duration:100000,Ambient:0,ShowParticles:1}]}

in a command block.
2. Activate the command block.

I am unsure of whether this is intended or bug. Thank you!