Firstly, TPC mod is independent of WBC. You need not mess with your original game whenever installing or reinstalling TPC. Saves a lot of time.
Secondly, this is not a bug report. Several units from the original game have been removed from direct production on purpose. We intend on balancing the races with fewer units and as the versions increase, add the other units (ogres, reapers and more) to the mix. Some however, will only be available through quests, temples, campaign, retinue etc.