Is there any other army with a rule like this? It seems extremely open to abuse to me - you could take one character and then fill out your army with the unit he makes cheaper, saving potentially hundreds of points and then the same army with the same units, but a different character that costs the same, would cost much more.
The standard way to represent a certain character being associated with certain units is making a Special choice Core instead. For instance, in my Zhatan rules, taking him allows Immortals to count as Core units.
Let’s hope they don’t go with that rule in this exact form then! If a rule like this is ever used, it has to affect just Special or Rare units for certain. You shouldn’t be able to get a whole army of discounted troops.
If that rumour is true, it’s more likely to be one unit of type X will be at -1pt per model. Or they get a piece of extra equipment free. I doubt it’d be all of one type of unit, unless it’s a special or rare…