Two things.
The addition of knigts didn't mean that Hungary forgot or didn't use the earlier methods.
In the other battles against western powers (Austria, complete HRE, czechs) they were still effective.
They seemed to use this kind of setup against Byzantium only in the beginning.
Also, while noone knows if Hungary had any heavy cavalry in steppe days (at least no metal armor was found by archeologists) it would not be a surprise if there were hungarian heavy cav before knights. At least huns, mongols used them, they also used them for frontal charges (in china) too.
I will pay attention to that part of the forum, great read!