unfortunately this seems to be true for all versions of Fireworks. I purchased the CS5 upgrade with the promise that this terrible use of points instead of pixels in FW would be resolved. I can assure you it is not.
this help page was also very lame as it first says FW default is Points, then says defaults to Pixels, then says you can change it, then says you can not change it. take a look.
Someone help..because FW only points, totally unacceptable. Im having to do my text by hand in html before I can accurately spec my image mocks because I cant tell my team what the pixel size of the font face is. and no, rendering text as paths does NOT give you an accurate unit of measure.
Don't fret! The default unit of text in Fireworks is pixels, not points.
The lack of units in FW can be confusing... and it can lead to sloppy thinking. And that particular Help page does more harm than good, because it appears to have been written for multiple applications, not just Fireworks. But if you read it with that in mind, you'll understand that Fireworks is the exception: it uses pixels as the unit for text size, and that unit cannot be changed in Preferences.
I confirmed this myself a while back, while playing with text at small sizes—including bitmap fonts, and vector fonts rendered without anti-aliasing. At the time, I thought, "Oh, pixels or points... what's the difference?" But it makes a big difference if you're dealing with a bitmap font that was designed to be rendered on an 8-pixel grid. It won't render properly if sized at 9 or 10 pixels... Anyway, points are generally larger than pixels, thanks to modern screen resolutions, and the two units are not equivalent. Fireworks is a bitmap editor, so it assumes you know that you're working with pixels, not points.