Evidently in 9E, they've changed how modifiers are combined by instituting a "MDAS" order, and then followed it up by an example that might show their intent, but doesn't make sense grammatically (at least to me). GW evidently wanted to nip the double dip of strength boosts and power gloves/thunder hammers, but still refer to those boosts as "increase the characteristic", not as a modifier to a roll. I thought it was pretty clear changing a characteristic was not the same as a roll modifier, as their interactions with resolving various formulas can make a notable difference, such as in their example.
They should have found better wording to make those boosts actual modifiers, such as "add one to strength when determining wound rolls" for the spell and "double strength when determining wound rolls" for the war gear. Now both are obviously modifiers, and their MDAS rule makes sense on how to resolve them.