So you're proposing that a single individual should be able to kill a heavy cav once he manages to stop him? Do you not see how wrong it is? The cavalry costs more and is already handicapped by the simple fact that it's a huge target that you can literally hear coming from the other side of the map and the only thing you gotta do 1v1 is listen, turn around in his direction and poke him. That's it, you're invulnerable to cav's attacks 1v1, unless you're really really bad. The real way for cavalry to capitalize on it's advantages is during teamfights, where, if you're with a competent team, you can easily just turn the tables against the cav using teamplay. There's literally nothing a cav can do head-on alone, even to an archer who can just shoot it while it tries to hit him.
No, I don't see how wrong it is.
The rider made a choice. That choice was to ride at considerable speed and head on to the opponent. They could've gone slower, and turned as they approached, sure, it'd make the stab harder to land and reduces damage but eliminates all chance of being reared. Being reared should come with severe consequences.
Those consequences could be an individual killing the rider, or an individual being able to fully kill a horse with spear, if it was moving at high velocity. Either way, a spear should have more velocity damage and pila should guaranteed one-shot to a charging horse to the head. If the rider's at speed to couch, the horse should be in velocity to get one-shot.
Perhaps you haven't been faced with a competent cavalryman in Bannerlord. Between horse head bobbing to absorb stabs and throws, quick deploying couches after shielding, low speed couching, bump stabs, and deceleration baiting to name a few techniques. I find it hard for you to say "you're invulnerable to cav's attacks 1v1", I feel this is a misrepresentation you've carried from Warband where most cavalry was not armoured, and it was indeed the case that, unless the rider was particularly exceptional, the cavalry would lose 1v1 mounted.
I agree, teamplay is the key to opposing cavalry and should be the most effective method. But team play alone should not be the only effective method of defeating a cavalry unit, otherwise low-to-mid tier games with little cohesion will be nothing more than cav spam festivals.
At a competitive level the armour values make rapid reaction throws redundant as they'd be better served guaranteed into an infantry for good damage, than possibly into a heavy horse for almost none. They make risking headons almost pointless due to glances, low rear reward, and potential one-shot, which ends with most blocking and attempting to dodge. But worse they consistently punish a single awareness mistake with an almost guaranteed one-shot kill, with the only equal course of retribution a perfectly placed headshot onto the charging cavalry, a significantly more difficult mechanical feat.
Consequences matter. Getting reared is a simple mechanical error, and it needs severe consequences, it is a severe misplay. The only way I see to do this is adjusting horse armour values and spear velocity damage parameters.