what is the resolution (DPI) of your PDF file ?
Image size: 2000x2100 pixels, DPI: 72 Pixels/Inch
I to have noticed this ins a few places and I usually get a message in comments on the css tab right next to the font size that says it's estimated due to a font substitution or something along those lines. But looking at the same font in other places that is smaller the font-size seems to be accurate. So for now it seems to only be wrong when the font size is very large (that particular font size is around 200px but in parfait it shows over 500)
I would like to take a look at the file. You can send me the file to corrinna @ adobe.com