The problem isn't that packed/blue ice doesn't mine faster with an efficiency pickaxe, but that they don't mine faster when using any pickaxe. Breaking packed ice by hand, breaking it with an unenchanted diamond pickaxe, and breaking it with an efficiency 5 diamond pickaxe all take the same amount of time.
Edit: I'm just going to add that this means that this bug has likely been present since packed ice began generating in ice spikes in 0.9, which is over 4 years old.
DoublePositive
The problem isn't that packed/blue ice doesn't mine faster with an efficiency pickaxe, but that they don't mine faster when using any pickaxe. Breaking packed ice by hand, breaking it with an unenchanted diamond pickaxe, and breaking it with an efficiency 5 diamond pickaxe all take the same amount of time.
Edit: I'm just going to add that this means that this bug has likely been present since packed ice began generating in ice spikes in 0.9, which is over 4 years old.