This is one of the most confusing things, the way it is on the cameras. The HVX200 and the HPX170 both can shoot progressive in 1080 but it is segmented frames. The cameras display it as 1080i/24pA and 10801/30p. Segmented frames is not the same thing as interlaced fields. The camera takes one solid frame and then breaks it up into 1/2 frames to write to the card. Then when you transfer the footage (if done correctly) your progressive segments are made into true progressive frames. So in FCP you have a true 23.98 or 29.97 progressive sequence.
2 Segmented frames = 1 progressive frame
2 interlaced fields DO NOT = 1 progressive frame.
If the camera was set on 1080i/24pA and you set the Log and Transfer pref to Removed duplicate frames or Advanced Pulldown, after the clips are transfered, they will be 23.98 in the bin.