This is true. Lots of incorrect specs for valve sizes, spring data, installed heights, etc.
I had a set of the cnc’d Victor copy BB heads here, advertised as 325cc.
Looking at them I could see they weren’t going to be that big.
Poured one...... it was about 25cc short.
I def wouldn’t assume the 179cc spec for the magnum replacements was correct.
It might be....... but it’s just as likely to not be.