The math works out a little bit differently

You’re right.

Currently, 0.75x0.75 (authors) and 0.75x0.25 (curators) of inflation.
Post-HF21, 0.65x0.50 and 0.65x0.50

So author rewards would be going from the current 56.25% of inflation to 32.5% of inflation, and curation rewards would change from the current 18.75% of inflation to 32.5% of inflation.