i think i understand what you are getting at, it would make sense if history repeated it self in the game.
but the problem is that by the time of Henry`s rule the realm in the game might have fared quite differently than the realm in real history. East Frankia might be on its last leg and units from lost parts of the realm would make no sense.
a military and organisational reform would not likely have come about if Regensburg(example) is all that is left.

that is why we decided that the reform should be tied to the success of the realm, rather than a rigid timeframe.
that said, there might have been set an earliest date for the convertion to HRE. if not one could in theory achieve empire with Louis the German.