The PHB is incapable of verifying Wally's statement, since he knows nothing about the matter.
This is exactly what Wally has aimed for, and since Wally is an engineer, a blanket denial by the PHB only serves to show up the fact that the PHB is less knowledgeable than his workers in the field.
One way that the PHB could verify Wally's statement is to ask someone more knowledgable than himself , such as Dilbert or Asok, whether Wally's assertion is true or even likely.
However, they have nothing to win and everything to loose by taking sides, so their answer will invariably be "It's hard to tell", or "I'm not sure".
Thus, without a clear refutation, Wally's statement made in the presence of others has to let stand, thus ensuring Wally's standing in the company for yet another season.