Thank you all for your fast replies. THis issue really concerned me last evening.
I re-read the rules and some accounts of the Battle of Hastings and absolutely agree with Paul's interpretation.
My friend also had 3 units of dismounted knights, but he used them to hold a defensive line while sending two units of mounted knights (with commanders) plus Breton skirmishers out on the flank similar to a tank spearhead. The skirmishers soon ran away, one knights got distracted and the last charging knights positioned badly, so only to bases got to fight. Probably not the best tactic...
Also we had to much terrain on board (8 pieces).
But in general I got him hooked on Swordpoint, just like myself
Next time it might be a more open battle and he'll probably rather use a combined arms approach and coordinate with his shooters.
I also think, that instead of getting stuck in melee with heavy infantry (a 4 turn stalemate!) disengaging for a new charge might be wise for Norman knights. The notion about widening the front rank for extra dice is very helpful, indeed. Hadn't thought about it like this.