Totyota also states that the electric motor outputs 33kW/44hp (see, for example, the booklet "2002 Prius"). So couldn't we just as logically state that the ICE output is 54 hp? (54 + 44 = 98). Again, how do we "know" that ICE=70hp is any more valid than electric=28hp or 44hp? Guess it depends on what you accept as the given.
I understand the distinction between total horsepower and available horsepower. I just wish that folks would use these numbers with a bit more precision and specificity.