The extent to which cavalry can and can't do variour things are very difficult to judge. I was reminded of this in the shower today when I was pondering whether or not Successor pikemen were armoured or not. I was thinking that they cannot have been overly vulnerable to missiles because they would never have sttod their ground.

Then I was reminded of the Napolionic wars.

Without knowing the level of training the men and horses had we can't know what they were capable of. It's possible that the horses were trained to charge home into semi-solid objects until they stopped baulking. It's also possible that the lancers themselves trained exhaustively in not sliding off their mounts at the point of contact.