Factory HP ratings -BS or what happened?

From its beginning (I think) the 225 slant was rated at 145hp. In 1972 it dropped to 110 hp and by '75 it's down to 95 hp. Are these number real or what where did the power go? (other engine sizes had big drops same years, but just looking at the 225 here)

I saw the recent dyno results on Power Nation slant build. They test the tired old engine at 70hp - OK, whatever. The reworked one with a four barrel and 8 degrees advance still only gives 130? How did a factory 1bbl ever give 145hp?